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/jobs.js

@@ -0,0 +1,63 @@
+import { getInstances, updateInstance, getConfig, setConfig } from './db.js';
+
+const TAILSCALE_API = 'https://api.tailscale.com/api/v2';
+
+let _interval = null;
+
+export async function runTailscaleSync() {
+  const apiKey  = getConfig('tailscale_api_key');
+  const tailnet = getConfig('tailscale_tailnet');
+  if (!apiKey || !tailnet) throw new Error('Tailscale not configured');
+
+  const res = await fetch(
+    `${TAILSCALE_API}/tailnet/${encodeURIComponent(tailnet)}/devices`,
+    { headers: { Authorization: `Bearer ${apiKey}` } }
+  );
+  if (!res.ok) throw new Error(`Tailscale API ${res.status}`);
+
+  const { devices } = await res.json();
+
+  // hostname -> first 100.x.x.x address
+  const tsMap = new Map(
+    devices.map(d => [d.hostname, (d.addresses ?? []).find(a => a.startsWith('100.')) ?? ''])
+  );
+
+  const instances = getInstances();
+  let updated = 0;
+
+  for (const inst of instances) {
+    const tsIp   = tsMap.get(inst.name);   // undefined = not in Tailscale
+    const matched = tsIp !== undefined;
+
+    const newTailscale = matched ? 1 : (inst.tailscale === 1 ? 0 : inst.tailscale);
+    const newIp        = matched ? tsIp : (inst.tailscale === 1 ? '' : inst.tailscale_ip);
+
+    if (newTailscale !== inst.tailscale || newIp !== inst.tailscale_ip) {
+      // Strip db-generated columns — node:sqlite rejects unknown named parameters
+      const { id: _id, created_at: _ca, updated_at: _ua, ...instData } = inst;
+      updateInstance(inst.vmid, { ...instData, tailscale: newTailscale, tailscale_ip: newIp });
+      updated++;
+    }
+  }
+
+  return { updated, total: instances.length };
+}
+
+export function restartJobs() {
+  if (_interval) { clearInterval(_interval); _interval = null; }
+  if (getConfig('tailscale_enabled') !== '1') return;
+
+  const mins = parseInt(getConfig('tailscale_poll_minutes', '15'), 10);
+  const ms   = Math.max(1, Number.isFinite(mins) ? mins : 15) * 60_000;
+
+  _interval = setInterval(async () => {
+    try {
+      const r = await runTailscaleSync();
+      setConfig('tailscale_last_run_at', new Date().toISOString());
+      setConfig('tailscale_last_result', `ok: ${r.updated} updated of ${r.total}`);
+    } catch (e) {
+      setConfig('tailscale_last_run_at', new Date().toISOString());
+      setConfig('tailscale_last_result', `error: ${e.message}`);
+    }
+  }, ms);
+}