feat: Refactor Poison system, implement Darkglow & Parasitic effects (#2385)

## Summary

- Refactors the poison system to separate `Index` (globally unique ID) from `Level` (tier within a family), enabling multiple poison families (Standard, Darkglow, Parasitic) to coexist without collisions
- Implements Darkglow and Parasitic poison special effects from Mondain's Legacy: Darkglow boosts damage by 10% when attacker is ranged, Parasitic heals the attacker for damage dealt in melee range
- Fixes several bugs: `Register()` crashing on duplicate `Level` values across families, `IncreaseLevel()` crossing family boundaries, `InfectiousStrike` and `NinjaWeapons` stripping poison family via level-based lookups, and `ArchCure`/`CleansingWinds` using raw `Level + 1` instead of `IncreaseLevel()`

## Changes

**`Projects/Server/Poison.cs`** — Adds `PoisonFamily` enum and abstract `Family` property. Adds `Index` as unique identifier. Fixes `Register()` to check `Index` uniqueness (not `Level`) and validate the new poison's name (not the existing one's). Fixes `IncreaseLevel()` to use `Index + 1`, naturally respecting family boundaries via Index gaps. Replaces linear name lookup with `Dictionary`-based `PoisonsByName`.

**`Projects/UOContent/Misc/Poison.cs`** — Adds `family` parameter to `PoisonImpl`. Implements Darkglow effect (10% damage boost when `From` >1 tile, cliloc 1072850) and Parasitic effect (heals `From` for damage dealt within 1 tile, cliloc 1060203) in `PoisonTimer.OnTick()`. Renames `m_` fields to `_` convention.

**`Projects/UOContent/Misc/PoisonKinds.cs`** — New file. Moves poison registration out of `PoisonImpl` into `PoisonKinds.Configure()`. Adds `PoisonFamily` to Darkglow/Parasitic registrations. Provides extension properties (`Lesser`, `Deadly`, `LesserDarkglow`, etc.), `GetPoison(int level)` (standard-only), `GetPoisonByFamilyAndLevel()`, and `IsDarkglow`/`IsParasitic` instance helpers.

**`Projects/UOContent/Items/Weapons/Abilities/InfectiousStrike.cs`** — Family-aware poison scaling: Darkglow caps at Deadly (Poisoning/33.3), Parasitic caps at Lethal (Poisoning/25), Standard unchanged. Level bump uses `IncreaseLevel()` with family boundary check.

**`Projects/UOContent/Items/Skill Items/Ninjitsu/NinjaWeapons.cs`** — EvilOmen level bump uses `Poison.IncreaseLevel()` instead of `Poison.GetPoison(Level + 1)`.

**`Projects/UOContent/Spells/Fourth/ArchCure.cs`** and **`CleansingWindsSpell.cs`** — Replace `poison.Level + 1` with `Poison.IncreaseLevel(poison).Level` for family-safe cure chance calculation.

**`Projects/Server/Serialization/SerializationExtensions.cs`** — Serializes/deserializes `Index` instead of `Level`.

**`DarkglowPotion.cs`** / **`ParasiticPotion.cs`** — Point to actual Darkglow/Parasitic poisons instead of placeholder `Greater`.

**`PotionKeg.cs`** / **`BasePotion.cs`** — Adds Darkglow, Parasitic, Invisibility, and FlintsPungentBrew to `PotionEffect` enum and keg label support.

## Test plan

- [ ] `dotnet build` compiles cleanly (verified, 0 warnings 0 errors)
- [ ] Verify `PoisonKinds.Configure()` registers all poisons without throwing (Register bug fix)
- [ ] Standard poison behavior unchanged — PoisonField, PoisonSpell, SerpentArrow, SavageShaman, TrappableContainer all use `GetPoison(int level)` which now correctly filters to Standard family
- [ ] Darkglow: poison tick deals +10% damage when attacker is >1 tile away, sends "Darkglow poison increases your damage!" message
- [ ] Parasitic: poison tick heals attacker for damage dealt when within 1 tile, sends heal message
- [ ] InfectiousStrike preserves poison family and respects family-specific skill scaling
- [ ] EvilOmen + NinjaWeapons level bump stays within poison family
- [ ] ArchCure/CleansingWinds cure chance calculations work correctly across all poison families
- [ ] Serialization round-trips correctly using Index

Projects/UOContent/Items/Skill Items/Magical/Misc/PotionKeg.cs

@@ -12,7 +12,9 @@ public partial class PotionKeg : Item
         TileData.ItemTable[0x1940].Height = 4;
     }
 
-    [InvalidateProperties] [SerializableField(0)] [SerializedCommandProperty(AccessLevel.GameMaster)]
+    [InvalidateProperties]
+    [SerializableField(0)]
+    [SerializedCommandProperty(AccessLevel.GameMaster)]
     private PotionEffect _type;
 
     [Constructible]
@@ -45,12 +47,20 @@ public partial class PotionKeg : Item
     {
         get
         {
-            if (_held > 0 && (int)_type >= (int)PotionEffect.Conflagration)
+            if (_held <= 0)
             {
-                return 1072658 + (int)_type - (int)PotionEffect.Conflagration;
+                return 1041641;
             }
 
-            return _held > 0 ? 1041620 + (int)_type : 1041641;
+            return _type switch
+            {
+                < PotionEffect.Nightsight or > PotionEffect.FlintsPungentBrew => 1041619,
+                PotionEffect.FlintsPungentBrew => 1113608,
+                >= PotionEffect.Parasitic => 1080069 + (int)_type - (int)PotionEffect.Parasitic,
+                PotionEffect.Invisibility => 1080071,
+                >= PotionEffect.Conflagration => 1072658 + (int)_type - (int)PotionEffect.Conflagration,
+                _ => 1041620 + (int)_type
+            };
         }
     }
 
@@ -249,6 +259,9 @@ public partial class PotionKeg : Item
             PotionEffect.ConflagrationGreater  => new GreaterConflagrationPotion(),
             PotionEffect.ConfusionBlast        => new ConfusionBlastPotion(),
             PotionEffect.ConfusionBlastGreater => new GreaterConfusionBlastPotion(),
+            PotionEffect.Invisibility          => new InvisibilityPotion(),
+            PotionEffect.Parasitic             => new ParasiticPotion(),
+            PotionEffect.Darkglow              => new DarkglowPotion(),
             _                                  => new NightSightPotion()
         };
 
@@ -279,6 +292,9 @@ public partial class PotionKeg : Item
             _ when type == typeof(GreaterConflagrationPotion)  => PotionEffect.ConflagrationGreater,
             _ when type == typeof(ConfusionBlastPotion)        => PotionEffect.ConfusionBlast,
             _ when type == typeof(GreaterConfusionBlastPotion) => PotionEffect.ConfusionBlastGreater,
-            _ /* when type == typeof(NightSightPotion) */      => PotionEffect.Nightsight
+            _ when type == typeof(InvisibilityPotion)          => PotionEffect.Invisibility,
+            _ when type ==  typeof(ParasiticPotion)            => PotionEffect.Parasitic,
+            _ when type ==  typeof(DarkglowPotion)             => PotionEffect.Darkglow,
+            _                                                  => PotionEffect.Nightsight
         };
 }

Projects/UOContent/Items/Skill Items/Magical/Potions/BasePotion.cs

@@ -35,7 +35,8 @@ public enum PotionEffect
     ConfusionBlastGreater,
     Invisibility,
     Parasitic,
-    Darkglow
+    Darkglow,
+    FlintsPungentBrew
 }
 
 [SerializationGenerator(2, false)]

Projects/UOContent/Items/Skill Items/Magical/Potions/Poison Potions/DarkglowPotion.cs

@@ -8,8 +8,7 @@ public partial class DarkglowPotion : BasePoisonPotion
     [Constructible]
     public DarkglowPotion() : base(PotionEffect.Darkglow) => Hue = 0x96;
 
-    /* public override Poison Poison => Poison.DarkGlow; // MUST be restored when prerequisites are done */
-    public override Poison Poison => Poison.Greater;
+    public override Poison Poison => Poison.GreaterDarkglow;
 
     public override double MinPoisoningSkill => 95.0;
     public override double MaxPoisoningSkill => 100.0;

Projects/UOContent/Items/Skill Items/Magical/Potions/Poison Potions/ParasiticPotion.cs

@@ -8,9 +8,10 @@ public partial class ParasiticPotion : BasePoisonPotion
     [Constructible]
     public ParasiticPotion() : base(PotionEffect.Parasitic) => Hue = 0x17C;
 
-    /* public override Poison Poison => Poison.Parasitic;  // MUST be restored when prerequisites are done */
-    public override Poison Poison => Poison.Greater;
+    public override Poison Poison => Poison.DeadlyParasitic;
 
     public override double MinPoisoningSkill => 95.0;
     public override double MaxPoisoningSkill => 100.0;
+
+    public override int LabelNumber => 1072848; // Parasitic Poison
 }

Projects/UOContent/Items/Skill Items/Ninjitsu/NinjaWeapons.cs

@@ -289,7 +289,7 @@ public static class NinjaWeapon
         {
             if (EvilOmenSpell.EndEffect(target))
             {
-                target.ApplyPoison(from, Poison.GetPoison(weapon.Poison.Level + 1));
+                target.ApplyPoison(from, Poison.IncreaseLevel(weapon.Poison));
             }
             else
             {