feat: Adds Feature Flag System (#2328)

## Feature Flag System

A runtime feature flag system for dynamically enabling/disabling game systems and blocking specific game elements
without server restarts.

### Overview

Two types of controls:

1. Feature Flags - Named boolean flags that gate entire systems (trading, PvP, vendors, housing, etc.)
2. Dynamic Blocks - Block specific gumps, items, skills, or spells by type

All changes are persisted to JSON, broadcast to online staff, and bypass-able by administrators.

### Predefined Flags
```
┌─────────────────┬──────────┬─────────────────────────────────────┐
│      Flag       │ Category │             Description             │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ player_trading  │ Economy  │ Allow secure trades between players │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ vendor_purchase │ Economy  │ Allow purchasing from NPC vendors   │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ vendor_sell     │ Economy  │ Allow selling to NPC vendors        │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ player_vendors  │ Economy  │ Allow player vendor interactions    │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ bank_access     │ Economy  │ Allow bank box access               │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ house_placement │ Housing  │ Allow new house placements          │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ boat_placement  │ Housing  │ Allow new boat placements           │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ bulk_orders     │ Crafting │ Allow bulk order deeds              │
├─────────────────┼──────────┼─────────────────────────────────────┤
│ pvp_combat      │ Combat   │ Allow player vs player combat       │
└─────────────────┴──────────┴─────────────────────────────────────┘
```

### Commands

#### Feature Flags
```
┌────────────────────────────────────────────────────┬───────────────────────┐
│                      Command                       │      Description      │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FeatureFlag <key> on|off|toggle|info              │ Manage a feature flag │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FF <key> on|off                                   │ Shorthand alias       │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FeatureFlag <key> create <category> <desc>        │ Create a custom flag  │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FeatureFlag <key> delete                          │ Delete a custom flag  │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FeatureList [flags|gumps|items|skills|spells|all] │ List all flags/blocks │
├────────────────────────────────────────────────────┼───────────────────────┤
│ [FeatureAdmin                                      │ Open the admin gump   │
└────────────────────────────────────────────────────┴───────────────────────┘
```

#### Gump Blocks
```
┌────────────────────────────────┬──────────────────────────────────────────────────────┐
│            Command             │                     Description                      │
├────────────────────────────────┼──────────────────────────────────────────────────────┤
│ [BlockGump <typeName> [reason] │ Block a gump type from displaying                    │
├────────────────────────────────┼──────────────────────────────────────────────────────┤
│ [UnblockGump <typeName>        │ Remove a gump block                                  │
├────────────────────────────────┼──────────────────────────────────────────────────────┤
│ [ListGumps [self]              │ List open gumps on a player (for finding type names) │
└────────────────────────────────┴──────────────────────────────────────────────────────┘
```

#### Item Blocks
```
┌────────────────────────────────────────────────┬───────────────────────────────┐
│                    Command                     │          Description          │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [BlockItemUse <typeName|target> [reason]       │ Block item use                │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [BlockItemEquip <typeName|target> [reason]     │ Block item equipping          │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [BlockItemContainer <typeName|target> [reason] │ Block container access        │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [UnblockItemUse <typeName>                     │ Remove use block              │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [UnblockItemEquip <typeName>                   │ Remove equip block            │
├────────────────────────────────────────────────┼───────────────────────────────┤
│ [UnblockItemContainer <typeName>               │ Remove container access block │
└────────────────────────────────────────────────┴───────────────────────────────┘
```
Item block commands create an entry if one doesn't exist, or flip the relevant flag on an existing entry. Unblock
commands only clear their specific flag -- the entry is removed when all flags (use/equip/container) are off.

#### Skill & Spell Blocks
```
┌──────────────────────────────────────┬──────────────────────┐
│               Command                │     Description      │
├──────────────────────────────────────┼──────────────────────┤
│ [BlockSkill <SkillName> [reason]     │ Block a skill        │
├──────────────────────────────────────┼──────────────────────┤
│ [UnblockSkill <SkillName>            │ Remove a skill block │
├──────────────────────────────────────┼──────────────────────┤
│ [BlockSpell <SpellTypeName> [reason] │ Block a spell        │
├──────────────────────────────────────┼──────────────────────┤
│ [UnblockSpell <SpellTypeName>        │ Remove a spell block │
└──────────────────────────────────────┴──────────────────────┘
```

### Architecture

- Static bool classes for hot-path checks (no dictionary lookups): ServerFeatureFlags (Server project) and
ContentFeatureFlags (UOContent)
- Synced automatically by FeatureFlagManager.SyncStaticFlag() when flags change
- Predefined flags loaded from Distribution/Configuration/FeatureFlags/default-flags.json
- Runtime state persisted to Configuration/FeatureFlags/*.json (flags, gump-blocks, item-blocks, skill-blocks,
spell-blocks)
- Admin gump with tabbed UI for managing all block types, per-entry PropertiesGump editing, and pagination
- All staff at AccessLevel.GameMaster+ bypass dynamic blocks; AccessLevel.Administrator+ bypass feature flags

### Hook Points

Hook: Player trading
Location: Mobile.OpenTrade
Mechanism: ServerFeatureFlags.PlayerTrading
────────────────────────────────────────
Hook: PvP combat
Location: Mobile.CanBeHarmful
Mechanism: ServerFeatureFlags.PvPCombat
────────────────────────────────────────
Hook: Bank access
Location: BankBox.Open()
Mechanism: ServerFeatureFlags.BankAccess
────────────────────────────────────────
Hook: Vendor buy/sell
Location: BaseVendor
Mechanism: ContentFeatureFlags.VendorPurchase/Sell
────────────────────────────────────────
Hook: Player vendors
Location: PlayerVendor
Mechanism: ContentFeatureFlags.PlayerVendors
────────────────────────────────────────
Hook: House placement
Location: HousePlacement.Check()
Mechanism: ContentFeatureFlags.HousePlacement (returns BadRegionTemp)
────────────────────────────────────────
Hook: Boat placement
Location: BaseBoatDeed.OnDoubleClick/OnPlacement
Mechanism: ContentFeatureFlags.BoatPlacement
────────────────────────────────────────
Hook: Bulk orders
Location: SmallBOD/LargeBOD
Mechanism: ContentFeatureFlags.BulkOrders
────────────────────────────────────────
Hook: Gump display
Location: GumpSystem.SendGump
Mechanism: FeatureFlagManager.IsGumpBlocked
────────────────────────────────────────
Hook: Item use
Location: PlayerMobile.AllowItemUse
Mechanism: FeatureFlagManager.IsItemUseBlocked
────────────────────────────────────────
Hook: Item equip
Location: PlayerMobile.CheckEquip
Mechanism: FeatureFlagManager.IsItemEquipBlocked
────────────────────────────────────────
Hook: Container access
Location: BaseContainer.DisplayTo
Mechanism: FeatureFlagManager.IsContainerAccessBlocked
────────────────────────────────────────
Hook: Skill use
Location: PlayerMobile.AllowSkillUse
Mechanism: FeatureFlagManager.IsSkillBlocked
────────────────────────────────────────
Hook: Spell casting
Location: Spell.Cast / Spellbook.CastSpellRequest
Mechanism: FeatureFlagManager.IsSpellBlocked

Projects/UOContent/Engines/Bulk Orders/SmallBOD.cs

@@ -3,6 +3,7 @@ using ModernUO.Serialization;
 using Server.Gumps;
 using Server.Items;
 using Server.Mobiles;
+using Server.Systems.FeatureFlags;
 
 namespace Server.Engines.BulkOrders;
 
@@ -69,14 +70,19 @@ public abstract partial class SmallBOD : BaseBOD
 
     public override void OnDoubleClick(Mobile from)
     {
-        if (IsChildOf(from.Backpack) || InSecureTrade || RootParent is PlayerVendor)
-        {
-            from.SendGump(new SmallBODGump(this));
-        }
-        else
+        if (!(IsChildOf(from.Backpack) || InSecureTrade || RootParent is PlayerVendor))
         {
             from.SendLocalizedMessage(1045156); // You must have the deed in your backpack to use it.
+            return;
         }
+
+        if (!ContentFeatureFlags.BulkOrders && from.AccessLevel < AccessLevel.Administrator)
+        {
+            from.SendMessage(0x22, "Bulk orders are temporarily disabled.");
+            return;
+        }
+
+        from.SendGump(new SmallBODGump(this));
     }
 
     public override void OnDoubleClickNotAccessible(Mobile from)