v0.5.0 - Wake-on-LAN + connectivity history

wol.py:
- build_magic_packet(): standard 6x0xFF + 16x MAC layout
- send_local_broadcast(): direct from container (ports 9 + 7 for safety)
- send_via_peer(): preferred path; SSHes to the OTHER Spark and runs a Python one-liner there so the packet originates on the target's LAN segment (most reliable)
- MAC validation + normalization

connectivity.py:
- /data/connectivity.json persistence (thread-safe, atomic rename)
- Stores per-Spark current state + last_change timestamp + rolling 200-event log
- Records up/down transitions; computes down_seconds / up_seconds durations
- MAC cache populated lazily during hardware probes

hardware.py:
- Probe now reads MAC via /sys/class/net/<default-route-iface>/address
- After each probe, record_state() emits a transition event if state changed
- record_mac() caches the address so WoL works when the Spark next goes down

Endpoints:
- GET /api/connectivity: macs, current state, last_change, events[]
- POST /api/spark/{name}/wake: tries via-peer first, falls back to direct broadcast

UI:
- Unreachable hardware card shows the cached MAC + 'Wake (WoL)' button (only if MAC known)
- New 'Connectivity log' button opens a modal with per-Spark transition history (last 25 each), including duration of each prior up/down period
- pollHardware also pulls /api/connectivity so WoL buttons appear without an extra fetch

Package: bump 0.5.0:0; main.ts sets CONNECTIVITY_LOG=/data/connectivity.json

image/app/static/index.html

@@ -26,8 +26,22 @@
     </section>
 
     <section id="hardware-panel" class="hardware-panel hidden">
-      <h2 class="section-title">Spark hardware</h2>
+      <div class="section-header">
+        <h2 class="section-title">Spark hardware</h2>
+        <button id="open-connectivity" class="btn small-btn">Connectivity log</button>
+      </div>
       <div id="hardware-grid" class="hardware-grid"></div>
+
+      <dialog id="connectivity-dialog" class="modal">
+        <form method="dialog" class="modal-form">
+          <h3>Spark connectivity history</h3>
+          <p class="muted small">Most recent up/down transitions per Spark. Tracked since this dashboard was installed.</p>
+          <div id="connectivity-content" class="connectivity-content"></div>
+          <div class="modal-actions">
+            <button type="button" id="connectivity-close" class="btn">Close</button>
+          </div>
+        </form>
+      </dialog>
     </section>
 
     <section id="endpoint-panel" class="endpoint-panel hidden">