feat: Implement Phase 5 Quest System (100% complete)

Add YAML-driven quest system with context-aware offering:

Core Implementation:
- Quest data models (Quest, QuestObjective, QuestReward, QuestTriggers)
- QuestService for YAML loading and caching
- QuestEligibilityService with level, location, and probability filtering
- LoreService stub (MockLoreService) ready for Phase 6 Weaviate integration

Quest Content:
- 5 example quests across difficulty tiers (2 easy, 2 medium, 1 hard)
- Quest-centric design: quests define their NPC givers
- Location-based probability weights for natural quest offering

AI Integration:
- Quest offering section in npc_dialogue.j2 template
- Response parser extracts [QUEST_OFFER:quest_id] markers
- AI naturally weaves quest offers into NPC conversations

API Endpoints:
- POST /api/v1/quests/accept - Accept quest offer
- POST /api/v1/quests/decline - Decline quest offer
- POST /api/v1/quests/progress - Update objective progress
- POST /api/v1/quests/complete - Complete quest, claim rewards
- POST /api/v1/quests/abandon - Abandon active quest
- GET /api/v1/characters/{id}/quests - List character quests
- GET /api/v1/quests/{quest_id} - Get quest details

Frontend:
- Quest tracker sidebar with HTMX integration
- Quest offer modal for accept/decline flow
- Quest detail modal for viewing progress
- Combat service integration for kill objective tracking

Testing:
- Unit tests for Quest models and serialization
- Integration tests for full quest lifecycle
- Comprehensive test coverage for eligibility service

Documentation:
- Reorganized docs into /docs/phases/ structure
- Added Phase 5-12 planning documents
- Updated ROADMAP.md with new structure

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

api/app/__init__.py

@@ -184,6 +184,11 @@ def register_blueprints(app: Flask) -> None:
     app.register_blueprint(shop_bp)
     logger.info("Shop API blueprint registered")
 
+    # Import and register Quests API blueprint
+    from app.api.quests import quests_bp
+    app.register_blueprint(quests_bp)
+    logger.info("Quests API blueprint registered")
+
     # TODO: Register additional blueprints as they are created
     # from app.api import marketplace
     # app.register_blueprint(marketplace.bp, url_prefix='/api/v1/marketplace')