v0.2.2 - spark-vllm-docker update checks + Apply Update

Backend:
- updates.py: get_update_status() runs git fetch + git rev-list --left-right --count HEAD...origin/main to learn ahead/behind/dirty, plus git log for pending commits
- UpdateManager class with asyncio.Lock; one update at a time
- POST /api/updates/apply triggers "git pull --ff-only && ./build-and-copy.sh -c" over SSH with streamed log + phase detection (Pulling / Building the vLLM container / Copying to peer Sparks)
- GET /api/updates returns {ok, behind, ahead, dirty, current, log[], branch}

Frontend:
- Persistent banner near footer: hidden when up-to-date, blue when N commits behind, warn (orange) when local dirty changes block update
- 'Show details' expands a list of pending commits
- 'Apply update' triggers the long-running build with phase + elapsed timer + collapsible logs
- Confirmation dialog explains the 5–40 min duration

Package: bump 0.2.2:0

image/app/static/index.html

@@ -116,6 +116,30 @@
       <section id="cards" class="cards"></section>
     </section>
 
+    <section id="update-banner" class="update-banner hidden">
+      <div class="ub-row">
+        <span id="ub-text">Checking for updates…</span>
+        <span class="spacer"></span>
+        <button id="ub-details" class="btn small-btn hidden">Show details</button>
+        <button id="ub-apply" class="btn small-btn primary hidden">Apply update</button>
+      </div>
+      <details id="ub-list" class="hidden">
+        <summary class="muted small">Pending commits</summary>
+        <pre id="ub-log" class="snippet"></pre>
+      </details>
+      <div id="ub-progress" class="hidden">
+        <div class="phase-row">
+          <div class="phase" id="ub-phase">Applying update…</div>
+          <span class="spacer"></span>
+          <span class="timer" id="ub-elapsed">0:00</span>
+        </div>
+        <details>
+          <summary class="muted small">Show technical logs</summary>
+          <pre id="ub-stream" class="log"></pre>
+        </details>
+      </div>
+    </section>
+
     <footer class="footer">
       <div class="health">
         <span class="health-item" id="h-vllm"><span class="dot"></span> vLLM</span>