feat: aider multi-provider credentials + test suite green (182/182)

aider_run multi-provider credentials (tools/aider.py):
- _resolve_credentials() — general credential resolver; replaces the previous
  OpenRouter-only injection; resolution priority: Anthropic model hint → explicit
  host_label → model prefix (openrouter/*, groq/*, deepseek/*, …) → OpenRouter
  default → Anthropic API key → any keyed cloud host → local/generic host
- _host_flags() — generates --api-key slug=key for known cloud providers (OpenRouter,
  OpenAI, Groq, Together, Fireworks, X.ai, DeepSeek, Mistral); generates
  --openai-api-base + --openai-api-key for generic/local hosts (Open WebUI, Ollama);
  appends /api suffix for openwebui host_type; auto-prefixes model with 'openai/'
  for generic endpoints when model has no / prefix
- Anthropic API keys from providers.anthropic.credentials (not a host entry)
- host_label param added to aider_run and FunctionDeclaration — pick a configured
  host by partial label match (e.g. 'OpenRouter', 'Local', 'scott-lt-i7-rtx')
- 16 unit tests for _resolve_credentials covering all resolution paths

main.py: move @app.get("/health") before app.include_router(ui.router) — the
/{username} catch-all in ui.router was swallowing the /health path

Test suite: 37 pre-existing failures → 182/182 passing
- test_tools.py: _task_list() missing priority arg (6 callsites); cron ID regex
  c_\w+ → c_[\w-]+ (token_urlsafe includes '-', causing intermittent truncation)
- test_webhooks.py: rewritten for per-user channel config architecture —
  patch routers.nextcloud_talk/google_chat.get_user_channels instead of removed
  settings fields; corrected endpoints /webhook/nextcloud/scott and
  /channels/google-chat/scott; non-empty cfg dicts so falsy-guard passes
- test_health.py: test_unknown_route_404 now uses 3-segment path (/{u}/{p}/x)
  since single-segment paths hit the /{username} UI catch-all
- test_api_files.py: removed '../config.py' from not-in-allowed test (ASGI
  normalizes it to /config.py which hits /{username} catch-all, not files router)
- test_security.py: same webhook patch target fix; per-user endpoint URLs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/tests/test_api_files.py

@@ -25,7 +25,10 @@ async def test_files_get_allowed(client):
 @pytest.mark.anyio
 async def test_files_get_not_in_allowed(client):
     """Files outside the ALLOWED set should return 404, not the file content."""
-    for name in ("TASKS.json", "CRONS.json", "SCRATCH.md", "../config.py", ".env"):
+    # Note: paths with '..' are normalized at the ASGI layer (e.g. /files/../config.py
+    # becomes /config.py which hits the /{username} UI catch-all, not the files router).
+    # Only test paths that stay within the files router's scope.
+    for name in ("TASKS.json", "CRONS.json", "SCRATCH.md", ".env"):
         r = await client.get(f"/files/{name}")
         assert r.status_code == 404, f"Expected 404 for {name}, got {r.status_code}"