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.

open-sse/handlers/chatCore/sseToJsonHandler.js

@@ -5,12 +5,12 @@ import { HTTP_STATUS } from "../../config/runtimeConfig.js";
 import { FORMATS } from "../../translator/formats.js";
 import { PROVIDERS } from "../../config/providers.js";
 import { buildRequestDetail, extractRequestConfig, saveUsageStats, formatDoneLine } from "./requestDetail.js";
+import { saveRequestDetail } from "@/lib/usageDb.js";
 import { ROLE, RESPONSES_ITEM } from "../../translator/schema/index.js";
 
 // Responses-API providers (e.g. codex) may emit SSE without content-type + use Responses output shape
 const isResponsesProvider = (p) =>
 	PROVIDERS[p]?.format === FORMATS.OPENAI_RESPONSES;
-import { saveRequestDetail, appendRequestLog } from "@/lib/usageDb.js";
 
 function textFromResponsesMessageItem(item) {
 	if (!item?.content || !Array.isArray(item.content)) return "";