feat: rebuild iOS app from API audit + new podcast/media service

iOS App (complete rebuild):
- Audited all fitness API endpoints against live responses
- Models match exact API field names (snapshot_ prefixes, UUID strings)
- FoodEntry uses computed properties (foodName, calories, etc.) wrapping snapshot fields
- Flexible Int/Double decoding for all numeric fields
- AI assistant with raw JSON state management (JSONSerialization, not Codable)
- Home dashboard with custom background, frosted glass calorie widget
- Fitness: Today/Templates/Goals/Foods tabs
- Food search with recent + all sections
- Meal sections with colored accent bars, swipe to delete
- 120fps ProMotion, iOS 17+ @Observable

Podcast/Media Service:
- FastAPI backend for podcast RSS + local audiobook folders
- Shows, episodes, playback progress, queue management
- RSS feed fetching with feedparser + ETag support
- Local folder scanning with mutagen for audio metadata
- HTTP Range streaming for local audio files
- Playback events logging (play/pause/seek/complete)
- Reuses brain's PostgreSQL + Redis
- media_ prefixed tables

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/media/app/api/deps.py

@@ -0,0 +1,21 @@
+"""API dependencies — auth, database session."""
+
+from fastapi import Header, HTTPException
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+
+
+async def get_user_id(
+    x_gateway_user_id: str = Header(None, alias="X-Gateway-User-Id"),
+) -> str:
+    """Extract authenticated user ID from gateway-injected header."""
+    if not x_gateway_user_id:
+        raise HTTPException(status_code=401, detail="Not authenticated")
+    return x_gateway_user_id
+
+
+async def get_db_session() -> AsyncSession:
+    """Provide an async database session."""
+    async for session in get_db():
+        yield session