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>

index.html

@@ -199,6 +199,31 @@
           <button class="btn btn-danger" onclick="importDB()">Import</button>
         </div>
       </div>
+      <div class="settings-section">
+        <div class="settings-section-title">Tailscale Sync</div>
+        <p class="settings-desc">Sync Tailscale status and IPs by matching device hostnames to instance names.</p>
+        <div class="settings-row" style="margin-bottom:12px">
+          <label class="settings-label" for="ts-enabled">Enable</label>
+          <input type="checkbox" id="ts-enabled" style="accent-color:var(--accent);width:14px;height:14px">
+        </div>
+        <div class="form-group">
+          <label class="form-label" for="ts-tailnet">Tailnet</label>
+          <input class="form-input" id="ts-tailnet" type="text" placeholder="e.g. Tt3Btpm6D921CNTRL">
+        </div>
+        <div class="form-group">
+          <label class="form-label" for="ts-api-key">API Key</label>
+          <input class="form-input" id="ts-api-key" type="password" placeholder="tskey-api-…">
+        </div>
+        <div class="form-group">
+          <label class="form-label" for="ts-poll">Poll Interval (minutes)</label>
+          <input class="form-input" id="ts-poll" type="number" min="1" placeholder="15">
+        </div>
+        <div class="settings-row" style="gap:8px;margin-bottom:8px">
+          <button class="btn btn-secondary" onclick="saveTailscaleSettings()">Save</button>
+          <button class="btn btn-secondary" id="ts-run-btn" onclick="runTailscaleNow()">Run Now</button>
+        </div>
+        <div id="ts-status" class="settings-desc" style="margin:4px 0 0;color:var(--text3)">—</div>
+      </div>
     </div>
   </div>
 </div>