refactor(claude-desktop): lock route IDs to sonnet/opus/haiku roles

Adapt to Claude Desktop 1.6259.1+ fail-all validation which only
accepts claude-(sonnet|opus|haiku)-* route IDs. Branded model names
(DeepSeek, Kimi, GLM, etc.) now live in a new labelOverride field
instead of being embedded in route IDs.

- Backend auto-repairs legacy unsafe routes to the next free
  sonnet/opus/haiku slot instead of erroring
- Frontend swaps the free-form route input for a role dropdown plus
  menu display name field
- Add CLAUDE_DESKTOP_ROLE_ROUTE_IDS as the single source of truth
  for role-to-route mapping; presets and form both consume it
- Drop the dead displayName alias on ClaudeDesktopModelRoute and the
  ineffective /v1/models display_name injection (UI ignores it)
- Update i18n (en/ja/zh) and form focus test for the new fields

src/types.ts

@@ -133,8 +133,7 @@ export interface AuthBinding {
 
 export interface ClaudeDesktopModelRoute {
   model: string;
-  /** @deprecated Claude Desktop ignores this in the model menu; kept only to read old configs. */
-  displayName?: string;
+  labelOverride?: string;
   supports1m?: boolean;
 }