fix(api): add PUT /api/settings/{key} endpoint and shared credentials for Google/Microsoft social login

- Add PUT /{key} endpoint to settings API with SettingValueUpdate body model (only
  requires value, key comes from URL path) — fixes 405 Method Not Allowed errors
  from the admin Connections wizard which used PUT to save settings
- Fix grey toggles on /admin/connections: they appeared grey because all saves were
  silently failing with 405; now saves succeed and toggles reflect actual state
- Add social_auth_google_use_global_credentials config field and auth.py logic to
  reuse google_drive_client_id/google_drive_client_secret for Google Sign-In
- Add social_auth_microsoft_use_global_credentials config field and auth.py logic to
  reuse onedrive_client_id/onedrive_client_secret for Microsoft Sign-In
- Also apply consistent both-field check for Dropbox global credentials fallback
- Add settings metadata entries for the two new boolean settings
- Add Google and Microsoft settings_keys to admin_connections service definitions
- Add JS visibility toggle logic for Google/Microsoft credential fields in admin UI
- Add 6 new unit/integration tests for PUT endpoint and SettingValueUpdate model

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
Agent-Logs-Url: https://github.com/christianlouis/DocuElevate/sessions/ac66041a-2cbd-4d90-8f8e-3588c629d4d8

app/views/settings.py

@@ -257,6 +257,7 @@ async def connections_page(request: Request, db: Session = Depends(get_db)):
                     "social_auth_google_enabled",
                     "social_auth_google_client_id",
                     "social_auth_google_client_secret",
+                    "social_auth_google_use_global_credentials",
                 ],
             }
         )
@@ -292,6 +293,7 @@ async def connections_page(request: Request, db: Session = Depends(get_db)):
                     "social_auth_microsoft_client_id",
                     "social_auth_microsoft_client_secret",
                     "social_auth_microsoft_tenant",
+                    "social_auth_microsoft_use_global_credentials",
                 ],
             }
         )