feat(sprint5): audit fixes — transactions, indexes, stat distribution, rest, forge cost

P0 — Race conditions fixées avec pessimistic_write transactions :
  combat (double-spend endurance), forge (double upgrade),
  craft (consumeMaterials atomique), equip (item swap).
Forge : coût or (50-1000) + endurance (15) ajouté.
Combat : item stat bonuses (force/agilite/intelligence/chance) appliqués.

P1 — Features manquantes :
  POST /api/characters/stats — distribution stat points (avec lock).
  POST /api/characters/rest — repos auberge (+50% HP, -20 endurance).
  Vitalité : +10 HP max par point distribué.

P2 — Indexes DB ajoutés :
  character_id sur character_items, character_materials, combat_logs,
  craft_jobs, player_achievements, community_contributions.
  Composite (characterId, materialId) sur character_materials.
  period sur hall_of_fame. achievement_id sur player_achievements.

P3 — Cleanup : @nestjs/jwt et pg retirés de package.json.

package.json

@@ -20,7 +20,6 @@
     "@nestjs/config": "^3.0.0",
     "@nestjs/core": "^10.0.0",
     "@nestjs/event-emitter": "^3.0.1",
-    "@nestjs/jwt": "^10.0.0",
     "@nestjs/platform-express": "^10.0.0",
     "@nestjs/throttler": "^5.0.0",
     "@nestjs/typeorm": "^10.0.0",
@@ -29,7 +28,6 @@
     "cookie-parser": "^1.4.6",
     "helmet": "^7.0.0",
     "mysql2": "^3.20.0",
-    "pg": "^8.11.0",
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",
     "typeorm": "^0.3.20"