feat: v0.1.4 — device intelligence dashboard

Add tabbed dashboard at /dashboard/ with three D3.js visualizations:
- Vendor treemap (devices grouped by type and vendor)
- SSID social graph (force-directed, shared probed SSIDs as edges)
- Fingerprint clusters (packed circles by device behavior)

Intelligence API endpoints at /api/v1/intelligence/ with param
validation. Dashboard built on htmx + Pico CSS dark theme + D3 v7,
all vendored locally (make vendor). 13 new tests (59 total).

templates/dashboard/partials/ssid_graph.html

@@ -0,0 +1,3 @@
+<div class="viz-container" id="ssid-graph"></div>
+<script src="{{ url_for('static', filename='js/viz/ssid_graph.js') }}"></script>
+<script>renderSsidGraph('#ssid-graph', '{{ url_for("api.ssid_graph") }}');</script>