fix: all 6 code review findings

1. admin.js: dashboard setTimeout was after return (dead code) — restructured
   to assign template to const html, run setTimeout, then return html

2. DockerManager.php createStack: replaced SELECT LAST_INSERT_ID() with
   db->insert() which already returns lastInsertId correctly for SQLite

3. DockerManager.php setQuota: replaced ON DUPLICATE KEY UPDATE / VALUES()
   MySQL syntax with SQLite-compatible ON CONFLICT(user_id) DO UPDATE SET
   excluded.col syntax

4. post-restore.sh: PHP helper file now written ONCE at start of step 4
   before any call to it (was written AFTER first call, causing silent failure)

5. post-restore.sh: git pull exit code now captured before pipeline (the
   while-read loop always exited 0, masking pull failures)

6. uninstall.sh: tar backup now aborts on failure (previously 2>/dev/null
   swallowed errors and rm -rf destroyed source unconditionally); also
   rm -f → rm -rf for .service.d drop-in directory

panel/public/assets/js/admin.js

@@ -124,7 +124,7 @@
 
     document.getElementById('server-ip').textContent = '';
 
-    return `
+    const html = `
 <div class="stats-grid">
   <div class="stat-card">
     <div class="stat-label">CPU Usage</div>
@@ -198,7 +198,9 @@
       : '<canvas id="dash-hist-chart" height="70"></canvas>'}
   </div>
 </div>`;
+    // setTimeout BEFORE return so it actually executes (after return is dead code)
     setTimeout(()=>{const c=document.getElementById('dash-hist-chart');if(!c||!hist.length)return;if(window.Chart){initStatsChart(c,hist);}else{const s2=document.createElement('script');s2.src='https://cdn.jsdelivr.net/npm/chart.js@4.4.0/dist/chart.umd.min.js';s2.onload=()=>initStatsChart(c,hist);document.head.appendChild(s2);}},150);
+    return html;
   }
 
   // ── Server Status ──────────────────────────────────────────────────────────