feat(claude-desktop): add 3P provider switching with proxy gateway

Adds a new ClaudeDesktop AppType that writes Claude Desktop's third-party
inference profile under configLibrary/, sharing _meta.json with other
launchers (Ollama-compatible) so cc-switch can coexist with them.

Two switch modes:
- direct: provider already exposes claude-* / anthropic/claude-* model
  ids on Anthropic Messages, Claude Desktop connects to it directly.
- proxy: cc-switch's local proxy acts as the inference gateway,
  presenting only claude-* route names to Claude Desktop and mapping
  them to real upstream models. Required after Anthropic restricted
  Claude Desktop to claude-family ids.

Backend:
- New module claude_desktop_config with snapshot/rollback, official seed
  bypass, /claude-desktop/v1/{models,messages} routes, and a single
  source of truth for default proxy routes.
- Gateway token persisted in SQLite, validated on every proxied request.
- get_claude_desktop_status surfaces drift signals (stale models,
  missing routes, proxy stopped, base URL mismatch, missing token).

Frontend:
- Slim ClaudeDesktopProviderForm independent from ProviderForm,
  controlled by a top-level appId guard.
- ProviderList banner consumes the status query (5s polling) and
  renders actionable diagnostics.
- ClaudeDesktopRouteToggle in the header to start/stop the local
  gateway without touching takeover state.
- Three-locale i18n synchronised.

src/config/appConfig.tsx

@@ -17,6 +17,7 @@ export interface AppConfig {
 
 export const APP_IDS: AppId[] = [
   "claude",
+  "claude-desktop",
   "codex",
   "gemini",
   "opencode",
@@ -45,6 +46,14 @@ export const APP_ICON_MAP: Record<AppId, AppConfig> = {
     badgeClass:
       "bg-orange-500/10 text-orange-700 dark:text-orange-300 hover:bg-orange-500/20 border-0 gap-1.5",
   },
+  "claude-desktop": {
+    label: "Claude Desktop",
+    icon: <ClaudeIcon size={14} />,
+    activeClass:
+      "bg-amber-500/10 ring-1 ring-amber-500/20 hover:bg-amber-500/20 text-amber-700 dark:text-amber-300",
+    badgeClass:
+      "bg-amber-500/10 text-amber-700 dark:text-amber-300 hover:bg-amber-500/20 border-0 gap-1.5",
+  },
   codex: {
     label: "Codex",
     icon: <CodexIcon size={14} />,