feat: add Settlement actor type with Overview/Buildings/Inventory tabs

- New TypeDataModel: archetype, territory, renown, currency (gp/sp/cp),
  garrison, underSiege, isCapital, founded, taxNotes, description, notes
- 3-tab ApplicationV2 sheet with drag & drop for building/weapon/armor/equipment
- Currency steppers (+/−), building constructed toggle, qty controls
- LESS-based CSS (settlement-sheet.less) + base.less updated for shared styles
- Full i18n keys in lang/en.json (8 settlement archetypes)
- system.json: registered settlement actor type

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

module/models/settlement.mjs

@@ -0,0 +1,40 @@
+import { SYSTEM } from "../config/system.mjs"
+
+export default class OathHammerSettlement extends foundry.abstract.TypeDataModel {
+  static defineSchema() {
+    const fields = foundry.data.fields
+    const requiredInteger = { required: true, nullable: false, integer: true }
+    const schema = {}
+
+    schema.description = new fields.HTMLField({ required: true, textSearch: true })
+    schema.notes        = new fields.HTMLField({ required: false, textSearch: true })
+
+    schema.archetype = new fields.StringField({
+      required: true,
+      nullable: false,
+      initial: "free-city",
+      choices: SYSTEM.SETTLEMENT_ARCHETYPES
+    })
+
+    schema.territory  = new fields.StringField({ required: true, nullable: false, initial: "" })
+    schema.founded    = new fields.StringField({ required: true, nullable: false, initial: "" })
+    schema.population = new fields.StringField({ required: true, nullable: false, initial: "" })
+
+    schema.renown = new fields.NumberField({ ...requiredInteger, initial: 0, min: 0 })
+
+    schema.currency = new fields.SchemaField({
+      gold:   new fields.NumberField({ ...requiredInteger, initial: 0, min: 0 }),
+      silver: new fields.NumberField({ ...requiredInteger, initial: 0, min: 0 }),
+      copper: new fields.NumberField({ ...requiredInteger, initial: 0, min: 0 })
+    })
+
+    schema.garrison   = new fields.StringField({ required: true, nullable: false, initial: "" })
+    schema.underSiege = new fields.BooleanField({ required: true, initial: false })
+    schema.isCapital  = new fields.BooleanField({ required: true, initial: false })
+    schema.taxNotes   = new fields.StringField({ required: true, nullable: false, initial: "" })
+
+    return schema
+  }
+
+  static LOCALIZATION_PREFIXES = ["OATHHAMMER.Settlement"]
+}