refactor: migrate main.py to modular routers and add project roadmap

- Migrated monolithic main.py to feature-scoped routers in app/routers/
- Added GEMINI.md for project context and AI instructional guidelines
- Updated README.md with a comprehensive modernization plan (SQL migration, robust scraping DSL, frontend modernization)
- Improved authentication with cookie support and modular JS
- Updated test suite and documentation

app/routers/router_static.py

@@ -0,0 +1,34 @@
+"""
+Static pages routes for Ohm Stream Downloader API.
+"""
+
+from fastapi import APIRouter, Request
+from fastapi.responses import RedirectResponse
+
+router = APIRouter(tags=["static"])
+
+
+def get_templates():
+    from main import templates
+
+    return templates
+
+
+@router.get("/web")
+async def web_interface(request: Request):
+    """Web interface"""
+    templates = get_templates()
+    return templates.TemplateResponse("index.html", {"request": request})
+
+
+@router.get("/login")
+async def login_page(request: Request):
+    """Login/Register page"""
+    templates = get_templates()
+    return templates.TemplateResponse("login.html", {"request": request})
+
+
+@router.get("/watchlist")
+async def watchlist_redirect():
+    """Redirect /watchlist to web interface with watchlist hash"""
+    return RedirectResponse("/web#watchlist")