Add Presence tab, RSSI chart, heartbeat; fix SSE flood, chart timezone, N+1 clients query

README.md

@@ -231,6 +231,10 @@ Open `http://192.168.1.133:8080` in your browser.
 - **RSSI history chart** — opens from any Networks row. Shows signal strength over time per node (1h / 2h / 6h / 24h selectable). Each node gets its own coloured line. Useful for spotting interference patterns, seeing how signal fluctuates by time of day, and comparing which node consistently hears a given AP better. Updates live as new scans arrive.
 - **Cross-node** — side-by-side per-node RSSI for every AP. Shows which node is physically closer to each network. Filter to multi-node only to focus on confirmed cross-node observations.
 - **Clients** — probe request data: unique MACs, vendor (OUI lookup), what SSIDs they're searching for, signal, which nodes saw them.
+- **Presence** — three sections driven entirely by probe data:
+  - *Present Now* — real (non-randomized) MACs seen 2+ times in the last hour. Filters out the city-center noise of transient devices.
+  - *New Arrivals* — devices and networks first seen in the last 24 hours, split into two side-by-side tables.
+  - *Regulars* — devices and networks seen on 2 or more distinct calendar days. Takes at least two days of data to populate.
 - **Node detail** — click a node in the sidebar for stats: total events, unique SSIDs/BSSIDs, RSSI range, first/last seen, uptime, free heap, AP signal, last 100 events.
 
 ### Sidebar
@@ -240,7 +244,7 @@ A node is considered **online** if a heartbeat was received within the last 30 s
 
 ### Live updates
 
-SSE stream pushes new beacon events as they arrive. The feed updates immediately. All other views (sidebar, networks, chart, cross-node) refresh on a 2-second debounce so a single scan burst doesn't flood the server with requests.
+SSE stream pushes new beacon events as they arrive. The feed updates immediately. All other views (sidebar, networks, chart, cross-node, presence) refresh on a 2-second debounce so a single scan burst doesn't flood the server with requests.
 
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@@ -277,7 +281,10 @@ The `oui.txt` file is the IEEE public OUI database (39,171 entries as of downloa
 - [x] Deployed to Orange Pi as systemd services (runs 24/7)
 - [x] All three nodes sending to Orange Pi, confirmed live
 - [x] Node heartbeat every 10s — uptime, free heap, AP signal, drives online/offline status
+- [x] RSSI history chart per network (canvas, per-node coloured lines, 1h/2h/6h/24h range)
+- [x] Presence tab — Present Now, New Arrivals, Regulars
 - [ ] Scan interval control from dashboard
+- [ ] DB pruning / retention policy (events.db grows indefinitely)
 
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