Initial scaffold: Nakama backend, Godot client, content schema

Sets up the Step 1 (Project Foundation) and Step 2 (Content Schemas) scaffold
from the implementation sequence. Includes Docker Compose stack, Nakama
TypeScript module stubs, PostgreSQL migration, Godot 4 project shell with
scene stubs and NakamaClient singleton, YAML content schemas for all entity
types, and example data for 3 characters, 2 jobs, and all 7 core resources.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

content/schema/banner.yaml

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+# banner.yaml — schema definition for gacha banner definitions
+#
+# All rate tables are content-driven. No hardcoded pull rates in server code.
+# Banner end dates and pity rules must be visible to players per design spec.
+
+$schema: "xyvera/content-schema/banner/v1"
+
+type: object
+required:
+  - id
+  - name
+  - type
+  - pull_cost
+  - pool
+  - pity
+
+properties:
+
+  id:
+    type: string
+    pattern: "^[a-z][a-z0-9_]*$"
+
+  name:
+    type: string
+
+  type:
+    type: string
+    enum: [standard, featured, event]
+    description: >
+      standard = permanent evergreen with wishlist;
+      featured = region or character banner with up/down rate;
+      event = limited mega-event with spark currency.
+
+  pull_cost:
+    type: object
+    required: [currency, single, multi]
+    properties:
+      currency:
+        type: string
+        description: "Resource ID used to pull. Usually 'diamond' or a banner-specific ticket."
+      single:
+        type: integer
+        minimum: 1
+      multi:
+        type: integer
+        minimum: 1
+        description: "Cost for a 10-pull. Typically single * 10 minus one free pull."
+
+  pool:
+    type: array
+    description: "All characters eligible from this banner."
+    items:
+      type: object
+      required: [character_id, rarity, base_weight]
+      properties:
+        character_id:
+          type: string
+        rarity:
+          type: string
+          enum: [R, SR, SSR, UR]
+        base_weight:
+          type: number
+          minimum: 0.0
+          description: "Relative weight before pity modifiers. Higher = more common."
+        is_featured:
+          type: boolean
+          default: false
+
+  pity:
+    type: object
+    required: [soft_pity_start, hard_pity, guaranteed_rarity]
+    properties:
+      soft_pity_start:
+        type: integer
+        minimum: 1
+        description: "Pull count at which SSR/UR rate starts increasing toward hard pity."
+      hard_pity:
+        type: integer
+        minimum: 1
+        description: "Pull count that guarantees at least guaranteed_rarity."
+      guaranteed_rarity:
+        type: string
+        enum: [SR, SSR, UR]
+      featured_guarantee:
+        type: object
+        description: "50/50 featured character guarantee rules."
+        properties:
+          rate:
+            type: number
+            minimum: 0.0
+            maximum: 1.0
+            description: "Chance featured character is selected when SSR hits."
+          guaranteed_after_loss:
+            type: boolean
+            default: true
+            description: "If false on the 50/50, next SSR is guaranteed featured."
+      spark_currency:
+        type: object
+        description: "Only applies to event-type banners."
+        properties:
+          currency_id:
+            type: string
+          spark_cost:
+            type: integer
+            description: "Amount of spark currency required to select a featured character."
+
+  active_from:
+    type: string
+    format: date-time
+    description: "ISO 8601 UTC datetime. Null means active from server start."
+
+  active_until:
+    type: string
+    format: date-time
+    description: "ISO 8601 UTC datetime. Null means permanent."
+
+  rerun_policy:
+    type: string
+    enum: [permanent, will_rerun, no_rerun_planned, collaboration_locked]
+    default: permanent
+    description: "Displayed to players per the fair-visibility design pillar."