refactor: fold hand-written serializable property setters into field hooks (#2587)

## Summary

Folds **113** hand-written `[SerializableProperty]` members into plain `[SerializableField]` declarations using the v4 setter hooks — value coercion/vetoes via `allowFieldChange`, post-change side effects via `fieldChanged` (whose `oldValue` parameter covers the old-house/old-sender unsubscribe patterns). Net **-450 lines** of setter boilerplate.

```cs
// before
[SerializableProperty(1)]
[CommandProperty(AccessLevel.GameMaster)]
public int Charges
{
    get => _charges;
    set
    {
        _charges = Math.Clamp(value, 0, MaxCharges);
        InvalidateProperties();
        this.MarkDirty();
    }
}

// after
[SerializableField(1, allowFieldChange: nameof(AllowChargesChange))]
[SerializedCommandProperty(AccessLevel.GameMaster)]
[InvalidateProperties]
private int _charges;

private bool AllowChargesChange(ref int value)
{
    value = Math.Clamp(value, 0, MaxCharges);
    return true;
}
```

## How sites were selected

A classifier parsed all 204 `[SerializableProperty]` sites and converted only those matching strict shapes: getter is exactly `get => _field;`, the assignment comes first (after at most an equality guard), and relocated side effects contain no `return`, no `value` mutation, and no field re-assignment. Everything else was left alone deliberately:

- **~34 custom getters** (fallback defaults like `_x == -1 ? Default : _x`, self-healing refs) — no setter hook can express these.
- **~35 pre-assignment logic** (durability Unscale/Scale sandwiches, old-state captures like PotionKeg's pile weight).
- **virtual/override members, name-mismatched backing fields (`m_`), exotic semantics** (guards' `Focus` does work on *equal* assignment; `ChampionSpawn.Active` never assigns its field).

Five sites the classifier refused were converted by hand where the hooks fit cleanly: `ReceiverCrystal.Sender`, `PlayerVendor.House`, `PlayerBarkeeper.House` (old-value unsubscribe via `oldValue`), `BaseSuit.AccessLevel` (its existing virtual `OnAccessLevelChanged` already had the exact callback shape), and `DyeTub.DyedHue` (a true veto: `AllowDyedHueChange(ref int value) => _redyable`).

## Verification

- Build: **0 errors, 0 warnings**.
- **Schema regeneration produces zero Migrations changes** — the conversion is wire- and schema-neutral by construction (same orders, types, and property names), and CI's schema diff check enforces it.
- **835 + 708 tests green.**

## Behavioral notes (all strict improvements, called out for review)

- Generated setters skip everything when the incoming value equals the current one; a few converted setters previously re-ran side effects on equal assignment (redundant `Update()`-style refreshes).
- Generated setters always `MarkDirty()` on change; several converted setters never did (e.g. `DyeTub.DyedHue`, `MorphItem` ranges) — their changes only persisted if something else dirtied the entity. Those latent persistence bugs are fixed by construction.

Projects/UOContent/Items/Deeds/DragonBardingDeed.cs

@@ -28,17 +28,14 @@ public partial class DragonBardingDeed : Item, ICraftable
 
     public override int LabelNumber => _exceptional ? 1053181 : 1053012; // dragon barding deed
 
-    [SerializableProperty(2)]
-    [CommandProperty(AccessLevel.GameMaster)]
-    public CraftResource Resource
+    [SerializableField(2, fieldChanged: nameof(OnResourceChanged))]
+    [SerializedCommandProperty(AccessLevel.GameMaster)]
+    [InvalidateProperties]
+    private CraftResource _resource;
+
+    private void OnResourceChanged(CraftResource oldValue, CraftResource newValue)
     {
-        get => _resource;
-        set
-        {
-            _resource = value;
-            Hue = CraftResources.GetHue(value);
-            InvalidateProperties();
-        }
+        Hue = CraftResources.GetHue(newValue);
     }
 
     public int OnCraft(