[Feature] Configurable starting gold amounts in Homebrew settings

Added `initialAmount` field to each currency type (coins, handfuls, bags, chests)
in the Homebrew settings schema. Defaults match book values (0, 1, 0, 0).

- Homebrew.mjs: added `initialAmount` NumberField per currency; `_initializeSource`
  coerces empty submissions to 0; `refreshConfig()` syncs values to
  `CONFIG.DH.RESOURCE.character.initialCurrency`
- resourceConfig.mjs: added mutable `initialCurrency` object on `character` export
- actorField.mjs: added `CharacterGoldField` subclass that reads initial values
  from config at actor creation time
- character.mjs: switched from `GoldField` to `CharacterGoldField`
- settings.hbs: restructured currency section to CSS Grid with column headers
  ("Quantity Name" / "Starting Amount") instead of per-field inline labels
- settings.less: added `.currency-rows` grid styles
- en.json: added `quantityName` and `initialAmount` localisation keys

styles/less/ui/settings/settings.less

@@ -201,6 +201,23 @@
         }
     }
 
+    .currency-rows {
+        display: grid;
+        grid-template-columns: auto 1fr 1fr auto;
+        gap: 4px;
+        align-items: center;
+        width: 100%;
+
+        .currency-header-label {
+            text-align: center;
+            font-size: var(--font-size-14);
+        }
+
+        input[type='checkbox'] {
+            justify-self: center;
+        }
+    }
+
     .settings-hint {
         width: 100%;
         display: flex;