feat: wire mobile app to real Timmy backend via JSON REST API (#73)

Add /api/chat, /api/upload, and /api/chat/history endpoints to the
FastAPI dashboard so the Expo mobile app talks directly to Timmy's
brain (Ollama) instead of a non-existent Node.js server.

Backend:
- New src/dashboard/routes/chat_api.py with 4 endpoints
- Mount /uploads/ for serving chat attachments
- Same context injection and session management as HTMX chat

Mobile app fixes:
- Point API base URL at port 8000 (FastAPI) instead of 3000
- Create lib/_core/theme.ts (was referenced but never created)
- Fix shared/types.ts (remove broken drizzle/errors re-exports)
- Remove broken server/chat.ts and 1,235-line template README
- Clean package.json (remove express, mysql2, drizzle, tRPC deps)
- Remove debug console.log from theme-provider

Tests: 13 new tests covering all API endpoints (all passing).

https://claude.ai/code/session_01XqErDoh2rVsPY8oTj21Lz2

Co-authored-by: Claude <noreply@anthropic.com>

src/dashboard/app.py

@@ -38,6 +38,7 @@ from dashboard.routes.hands import router as hands_router
 from dashboard.routes.grok import router as grok_router
 from dashboard.routes.models import router as models_router
 from dashboard.routes.models import api_router as models_api_router
+from dashboard.routes.chat_api import router as chat_api_router
 from infrastructure.router.api import router as cascade_router
 
 logging.basicConfig(
@@ -185,6 +186,15 @@ app.add_middleware(
 templates = Jinja2Templates(directory=str(BASE_DIR / "templates"))
 app.mount("/static", StaticFiles(directory=str(PROJECT_ROOT / "static")), name="static")
 
+# Serve uploaded chat attachments (created lazily by /api/upload)
+_uploads_dir = PROJECT_ROOT / "data" / "chat-uploads"
+_uploads_dir.mkdir(parents=True, exist_ok=True)
+app.mount(
+    "/uploads",
+    StaticFiles(directory=str(_uploads_dir)),
+    name="uploads",
+)
+
 app.include_router(health_router)
 app.include_router(agents_router)
 app.include_router(swarm_router)
@@ -212,6 +222,7 @@ app.include_router(hands_router)
 app.include_router(grok_router)
 app.include_router(models_router)
 app.include_router(models_api_router)
+app.include_router(chat_api_router)
 app.include_router(cascade_router)