feat: Tailscale sync jobs

Adds a background job system that polls the Tailscale API on a configurable
interval and syncs tailscale status and IPs to instances by hostname match.

- New config table (key/value) in SQLite for persistent server-side settings
- New server/jobs.js: runTailscaleSync + restartJobs scheduler
- GET/PUT /api/config — read and write Tailscale settings; API key masked as **REDACTED** on GET
- POST /api/jobs/tailscale/run — immediate manual sync
- Settings modal: new Tailscale Sync section with enable toggle, tailnet, API key, poll interval, Save + Run Now buttons, last-run status

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/server.js

@@ -3,6 +3,7 @@ import helmet from 'helmet';
 import { fileURLToPath } from 'url';
 import { dirname, join } from 'path';
 import { router } from './routes.js';
+import { restartJobs } from './jobs.js';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const PORT = process.env.PORT ?? 3000;
@@ -47,5 +48,6 @@ app.use((err, _req, res, _next) => {
 
 // Boot — only when run directly, not when imported by tests
 if (process.argv[1] === fileURLToPath(import.meta.url)) {
+  restartJobs();
   app.listen(PORT, () => console.log(`catalyst on :${PORT}`));
 }