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/utils/settings_service.py

@@ -303,6 +303,20 @@ SETTING_METADATA = {
         "required": False,
         "restart_required": True,
     },
+    "social_auth_google_use_global_credentials": {
+        "category": "Social Login",
+        "description": (
+            "When True, Google social login uses the global GOOGLE_DRIVE_CLIENT_ID / "
+            "GOOGLE_DRIVE_CLIENT_SECRET credentials (the Google Drive OAuth integration) "
+            "instead of requiring separate SOCIAL_AUTH_GOOGLE_CLIENT_ID / "
+            "SOCIAL_AUTH_GOOGLE_CLIENT_SECRET values. "
+            "Requires SOCIAL_AUTH_GOOGLE_ENABLED=True and global Google Drive OAuth credentials to be set."
+        ),
+        "type": "boolean",
+        "sensitive": False,
+        "required": False,
+        "restart_required": True,
+    },
     "social_auth_microsoft_enabled": {
         "category": "Social Login",
         "description": (
@@ -345,6 +359,20 @@ SETTING_METADATA = {
         "required": False,
         "restart_required": True,
     },
+    "social_auth_microsoft_use_global_credentials": {
+        "category": "Social Login",
+        "description": (
+            "When True, Microsoft social login uses the global ONEDRIVE_CLIENT_ID / "
+            "ONEDRIVE_CLIENT_SECRET credentials (the OneDrive integration credentials) "
+            "instead of requiring separate SOCIAL_AUTH_MICROSOFT_CLIENT_ID / "
+            "SOCIAL_AUTH_MICROSOFT_CLIENT_SECRET values. "
+            "Requires SOCIAL_AUTH_MICROSOFT_ENABLED=True and global OneDrive credentials to be set."
+        ),
+        "type": "boolean",
+        "sensitive": False,
+        "required": False,
+        "restart_required": True,
+    },
     "social_auth_apple_enabled": {
         "category": "Social Login",
         "description": (