Add dynamic UART/BLE host connect for serve, dashboard, and WS.

Serve starts without a required port; REST/WS/UI can scan and switch transports, with BLE live ticks and UART-only OTA.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/docs/API_REST.md

@@ -1,6 +1,6 @@
 # REST API
 
-`go run . -port /dev/ttyUSB0 serve` starts two HTTP servers on the same UART link:
+`go run . serve` (optional `-port` / `-ble`) starts two HTTP servers on the same `managedHost` (UART or BLE):
 
 | Base URL | Flag | Used by |
 |----------|------|---------|
@@ -27,6 +27,9 @@ GET /api/v1/
   "name": "powerpod-external-api",
   "version": "1",
   "serial_port": "/dev/ttyUSB0",
+  "transport": "uart",
+  "endpoint": "/dev/ttyUSB0",
+  "connected": true,
   "websocket": "/ws",
   "default_interval_ms": 16,
   "min_interval_ms": 1,
@@ -110,7 +113,34 @@ WebSocket: `set_led_ring` with the same fields plus `"type":"set_led_ring"` →
 
 Used by the web UI; safe for scripts that drive the same features.
 
-### Live stream (host `CACHE_STATUS` poll ~16 ms)
+### Host link (UART / BLE)
+
+```http
+GET /api/host
+→ {"transport":"none|uart|ble","endpoint":"…","connected":false,"ble_name":""}
+
+GET /api/serial/ports
+→ {"ports":["/dev/ttyUSB0",…]}
+
+POST /api/host/connect
+Content-Type: application/json
+{"transport":"uart","port":"/dev/ttyUSB0"}
+{"transport":"ble","address":"AA:BB:…","name":"Powerpod"}
+
+POST /api/host/disconnect
+
+POST /api/ble/scan
+{"timeout_s":5,"name_filter":"Powerpod"}
+→ {"devices":[{"address":"…","name":"Powerpod","rssi":-55}]}
+```
+
+`name_filter` is optional substring match (case-insensitive); omit to list all LE advertisements. Active BLE is disconnected before scan (BlueZ adapter).
+
+Dashboard WebSocket state includes `host_connected`, `host_transport`, `host_endpoint` (aliases `uart_connected` / `serial_port` kept).
+
+**OTA** (`POST /api/ota`) returns **400** unless `transport==uart` and connected.
+
+### Live stream (host `CACHE_STATUS` poll ~16 ms; BLE uses `BLE_STREAM_TICK`)
 
 ```http
 GET /api/live-stream