feat(05-01): add Phase 5 cloud storage packages and config settings

- Add 6 new packages to requirements.txt: cryptography>=41.0.0,
  google-auth-oauthlib>=1.3.1, google-api-python-client>=2.196.0,
  msal>=1.36.0, webdavclient3>=3.14.7, cachetools>=5.3.0
- Add 8 new Settings fields to config.py: cloud_creds_key,
  google_client_id/secret, onedrive_client_id/secret/tenant_id,
  backend_url (frontend_url already present from Phase 2)
- Append cloud storage section to .env.example

backend/config.py

@@ -56,5 +56,19 @@ class Settings(BaseSettings):
     default_ai_provider: str = "ollama"  # DEFAULT_AI_PROVIDER env var
     default_ai_model: str = "llama3.2"   # DEFAULT_AI_MODEL env var
 
+    # Cloud Storage (Phase 5)
+    # master key for HKDF per-user credential encryption — must be overridden in production
+    cloud_creds_key: str = "CHANGEME-32-bytes-padded!!"
+    google_client_id: str = ""
+    google_client_secret: str = ""
+    onedrive_client_id: str = ""
+    onedrive_client_secret: str = ""
+    # "common" works for both personal and org accounts
+    onedrive_tenant_id: str = "common"
+    # used to construct OAuth callback URLs (e.g. {backend_url}/api/cloud/google/callback)
+    backend_url: str = "http://localhost:8000"
+    # used to construct OAuth success/error redirect to Vue app (per Phase 5 B4 fix)
+    # Note: frontend_url already declared above for Phase 2 (password reset links) — shared field
+
 
 settings = Settings()