feat(dashboard): per-key model restrictions, pin header routing, combo side-panel picker

- Endpoint: per-API-key model allowlist (schema v3) enforced on chat (403)
  and /v1/models; Full-access toggle + multi-select picker in Keys UI.
- Providers: honor x-connection-id in /v1/chat/completions — pinned requests
  no longer rotate to another account on failure.
- Providers: strategy saves merge into stored enabled:false override;
  Test All groups match grid sections; 1-by-1 skips disabled connections.
- Dashboard: provider-card toggle syncs from server on failure; grid toggles
  always visible; connection rows get clear-✕ for stale error banners.
- Combo editor: on desktop (xl+) the Add-Model picker opens as a floating
  side panel beside the untouched combo popup instead of stacking on top;
  mobile keeps the full-screen overlay.
- Long API-key overflow fixed in key rows + provider model sections.

tests/unit/github-monthly-usage-lock.test.js

@@ -14,7 +14,7 @@ vi.mock("@/shared/constants/providers.js", () => ({
   FREE_PROVIDERS: {},
   resolveProviderId: (provider) => provider,
 }));
-vi.mock("@/sse/utils/logger.js", () => ({ debug: vi.fn(), info: vi.fn(), warn: vi.fn() }));
+vi.mock("@/sse/utils/logger.js", () => ({ debug: vi.fn(), info: vi.fn(), warn: vi.fn(), error: vi.fn() }));
 
 const { markAccountUnavailable } = await import("../../src/sse/services/auth.js");