feat(headroom): add proxy lifecycle management + dashboard UI

Build on the optional Headroom Token Saver from Carmelo Campos
(PR: feat: add optional Headroom token saver). Add managed start/stop
of the local headroom proxy from the dashboard, install detection,
status probing, and a simplified Token Saver UI.

- detect headroom CLI + python>=3.10, probe proxy /health
- spawn/stop proxy as a detached, pid-tracked process
- /api/headroom/{status,start,stop} routes, gated local-only in dashboardGuard
- one-click Start/Stop Headroom modal, no manual config needed
- claude<->openai shape conversion for /v1/compress via 9router translators

Thanks to Carmelo Campos (@carmelogunsroses) for the original Headroom integration.

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/providers/registry/deepseek.js

@@ -1,3 +1,5 @@
+import { CLAUDE_API_HEADERS } from "../shared.js";
+
 export default {
   id: "deepseek",
   priority: 110,
@@ -24,6 +26,20 @@ export default {
       scope: "all",
     },
   },
+  // Multi-endpoint: pick the transport matching client sourceFormat to skip translation.
+  transports: [
+    {
+      format: "openai",
+      baseUrl: "https://api.deepseek.com/chat/completions",
+      auth: { combined: true, header: "Authorization", scheme: "bearer" },
+    },
+    {
+      format: "claude",
+      baseUrl: "https://api.deepseek.com/anthropic/v1/messages",
+      headers: { ...CLAUDE_API_HEADERS },
+      auth: { combined: true, header: "x-api-key", scheme: "raw" },
+    },
+  ],
   models: [
     { id: "deepseek-v4-pro", name: "DeepSeek V4 Pro" },
     { id: "deepseek-v4-pro-max", name: "DeepSeek V4 Pro Max", upstreamModelId: "deepseek-v4-pro" },