feat(plugins): plugins framework + per-API-key disable-non-public-models (#3041)

Integrates two community contributions into release/v3.8.8 with security hardening and conflict resolution.

- **Plugins framework** (#2913 — thanks @oyi77): hooks + registry unification, plugin SDK (`definePlugin`), worker-thread sandbox, per-plugin hook rate limiting, SHA-256 integrity verification, semver-gated upgrade, and execution analytics. Plugin routes are loopback-only (`isLocalOnlyPath`); `child_process` exec is opt-in via `OMNIROUTE_PLUGINS_ALLOW_EXEC` (default off).
- **API key option: disable non-published models** (#3017 — thanks @androw): a per-key flag restricting the key to discovered public models (combos / `auto/*` / `qtSd/*` routing still allowed).

Hardening applied during integration: migration renumber (089/090/091), `/api/plugins` LOCAL_ONLY route-guard classification (closes the plugin-RCE vector), atomic install/upgrade with path containment, `O_EXCL` tmp-file creation (TOCTOU), rate-limit-map eviction, `validatePluginConfig` on configure, `buildErrorBody` on all plugin error paths. 246/246 tests; typecheck / cycles / docs-sync clean.

Co-authored-by: oyi77 <14921983+oyi77@users.noreply.github.com>
Co-authored-by: Nicolas Lorin <androw95220@gmail.com>

src/app/api/plugins/scan/route.ts

@@ -1,5 +1,6 @@
 import { NextRequest, NextResponse } from "next/server";
 import { CORS_HEADERS, handleCorsOptions } from "@/shared/utils/cors";
+import { buildErrorBody } from "@omniroute/open-sse/utils/error";
 import { pluginManager } from "@/lib/plugins/manager";
 import { requireManagementAuth } from "@/lib/api/requireManagementAuth";
 
@@ -19,7 +20,11 @@ export async function POST(request: NextRequest) {
       { discovered: result.discovered, errors: result.errors },
       { headers: CORS_HEADERS }
     );
-  } catch (err: any) {
-    return NextResponse.json({ error: err.message }, { status: 500, headers: CORS_HEADERS });
+  } catch (err: unknown) {
+    console.error("[plugins] Failed to scan plugin directory:", err);
+    return NextResponse.json(buildErrorBody(500, "Failed to scan plugin directory"), {
+      status: 500,
+      headers: CORS_HEADERS,
+    });
   }
 }