feat(settings): hide API key from frontend, use status+edit instead of password field

Backend changes:
- Add civitai_api_key to _NO_SYNC_KEYS, return only boolean civitai_api_key_set
- Clean up known template placeholder on load to prevent false positive

Frontend changes:
- Replace type=password with type=text + CSS masking (-webkit-text-security)
- Replace pre-filled input with status display (Configured/Not configured)
- Add inline edit view with Save/Cancel buttons
- Re-add eye toggle via CSS class toggle (not type switching)
- Use CSS transitions for smooth status/edit view switching

This prevents Chromium/Vivaldi password manager from triggering
'save password' prompts when opening the settings modal.

py/services/settings_manager.py

@@ -134,6 +134,9 @@ class SettingsManager:
         self._template_path = (
             Path(__file__).resolve().parents[2] / "settings.json.example"
         )
+        # Known placeholder value in settings.json.example; any file containing
+        # this value should be treated as "not configured".
+        self._TEMPLATE_PLACEHOLDER_API_KEY = "your_civitai_api_key_here"
         self.settings = self._load_settings()
         self._migrate_setting_keys()
         self._ensure_default_settings()
@@ -165,6 +168,12 @@ class SettingsManager:
                     self._original_disk_payload = copy.deepcopy(data)
                     if self._matches_template_payload(data):
                         self._preserve_disk_template = True
+                    # Clean up the template placeholder so it is not treated
+                    # as a real key (affects both the frontend boolean and
+                    # the downloader's Authorization header).
+                    placeholder = self._TEMPLATE_PLACEHOLDER_API_KEY
+                    if data.get("civitai_api_key") == placeholder:
+                        data["civitai_api_key"] = ""
                 return data
             except json.JSONDecodeError as exc:
                 logger.error("Failed to parse settings.json: %s", exc)