[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

lang/en.json

@@ -2887,7 +2887,9 @@
                     "iconName": "Icon Name",
                     "iconNameHint": "Icons are from fontawesome",
                     "bagName": "Bag Name",
-                    "chestName": "Chest Name"
+                    "chestName": "Chest Name",
+                    "quantityName": "Quantity Name",
+                    "initialAmount": "Starting Amount"
                 },
                 "domains": {
                     "domainsTitle": "Base Domains",