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/data/quests/easy/cellar_rats.yaml

@@ -0,0 +1,109 @@
+# Cellar Rats - Entry level quest for new players
+quest_id: quest_cellar_rats
+name: "Rat Problem in the Cellar"
+description: |
+  Giant rats have infested the Rusty Anchor's cellar, threatening
+  the tavern's food supplies and scaring away customers. Grom the
+  bartender needs someone to clear them out.
+difficulty: easy
+
+# NPC Quest Givers (quest-centric design)
+quest_giver_npc_ids:
+  - npc_grom_ironbeard
+quest_giver_name: "Grom Ironbeard"
+
+# Location context
+location_id: crossville_tavern
+region_id: crossville
+
+# Offering conditions
+offering_triggers:
+  location_types: ["tavern"]
+  specific_locations: ["crossville_tavern"]
+  min_character_level: 1
+  max_character_level: 5
+  required_quests_completed: []
+  probability_weights:
+    tavern: 0.35
+    town: 0.15
+
+# NPC-specific offer dialogue
+npc_offer_dialogues:
+  npc_grom_ironbeard:
+    dialogue: |
+      *leans in conspiratorially* Got a problem, friend. Giant rats
+      in me cellar. Been scaring off the paying customers and getting
+      into the ale stores. 50 gold for whoever clears 'em out.
+    conditions:
+      min_relationship: 30
+      required_flags: []
+      forbidden_flags: ["refused_rat_quest"]
+
+# What NPCs know about this quest
+npc_quest_knowledge:
+  npc_grom_ironbeard:
+    - "The rats started appearing about a week ago"
+    - "They seem bigger than normal rats - something's not right"
+    - "Old smuggling tunnels under the cellar might be where they're coming from"
+    - "Lost three kegs of dwarven stout to the vermin already"
+
+# Embedded lore for AI context
+lore_context:
+  backstory: |
+    The cellar of the Rusty Anchor connects to old smuggling tunnels
+    from Captain Morgath's days, sealed decades ago. Recent earthquakes
+    may have reopened them, allowing creatures to emerge.
+  world_connections:
+    - "The earthquakes that opened the tunnels also disturbed the Old Mines"
+    - "Giant rats are unnatural - possibly corrupted by dark magic from below"
+  regional_hints:
+    - "Smuggling was common 50 years ago in Crossville"
+    - "Captain Morgath was a notorious smuggler who disappeared mysteriously"
+
+# Narrative hooks for natural dialogue
+dialogue_templates:
+  narrative_hooks:
+    - "mentions unusual scratching sounds from below"
+    - "complains about spoiled food supplies"
+    - "nervously glances toward the cellar door"
+    - "asks if you've ever dealt with vermin before"
+  ambient_hints:
+    - "You notice scratch marks near the cellar door"
+    - "A faint squeaking echoes from somewhere below"
+    - "The air carries a musty, unpleasant odor"
+
+# Objectives
+objectives:
+  - objective_id: kill_rats
+    description: "Clear out the giant rats"
+    objective_type: kill
+    required_progress: 10
+    target_enemy_type: giant_rat
+
+  - objective_id: find_source
+    description: "Discover where the rats are coming from"
+    objective_type: discover
+    required_progress: 1
+    target_location_id: smuggler_tunnel_entrance
+
+# Rewards
+rewards:
+  gold: 50
+  experience: 100
+  items: []
+  relationship_bonuses:
+    npc_grom_ironbeard: 10
+  unlocks_quests: ["quest_tunnel_mystery"]
+  reveals_locations: ["crossville_tunnels"]
+
+# Completion dialogue
+completion_dialogue:
+  npc_grom_ironbeard: |
+    *actually smiles* Well done, friend! Rats are gone, cellar's safe.
+    Here's your coin, well earned. Drink's on the house tonight.
+    *pauses* You say you found old tunnels down there? Interesting...
+
+tags:
+  - starter
+  - combat
+  - exploration