Phase 03: CAM decode coverage, real sensor data in TX, V2X monitor for ESP32 path

CAM codec:
- Stop rejecting CAMs carrying a specialVehicleContainer. It is declared last in
  CamParameters, after everything this decoder reads, so buses / emergency
  vehicles / road-works vehicles now decode for position and kinematics instead
  of being dropped outright
- Drop the lowFrequencyContainer parse - it extracted nothing into Cam, and its
  reads were only correct when no high-frequency optionals were present
- Document why the 7 optional-presence bits are consumed but not acted on: UPER
  writes a SEQUENCE's presence bitmap up front but each field's value in
  declaration order, and all seven are declared after yawRate
- Field widths and container ordering verified against the ETSI ASN.1 sources in
  the C-ITS-Parser checkout, not from memory

Transmit path:
- Own StationID is now a persisted random 32-bit value instead of a hardcoded 0.
  Receivers key on StationID to track a station across CAMs, so every unit
  broadcasting 0 made two MicrOBUs indistinguishable - including to this app's
  own detection engine
- Populate longitudinalAcceleration from successive GNSS speed samples. Not from
  the accelerometer: CAM wants signed along-track acceleration, and the raw
  sensor is device-frame with gravity in it. Null outside a usable sample gap
  rather than a fabricated value
- CAM pinger builds from live GNSS/IMU via PhoneCamBuilder instead of beaconing a
  hardcoded bench coordinate with speed and heading pinned to zero, so it now
  exercises the sensor pipeline and not just the wire. Sends nothing without a
  fix, and reports that rather than sitting at "Sent: 0"

V2X monitor:
- Received-CAM pane for the ESP32-C5 path, replacing the MQTT topic list that is
  permanently empty there. One row per station rather than per message - CAMs
  arrive at 1-10 Hz per station, so the pane is bounded by road users nearby, not
  by traffic rate. Nearest first, tinted by active alert level
- DENM hazard pins on the live map as a warning triangle, drawn above vehicle
  markers. CiT One path only: the ESP32 firmware forwards BTP-B port 2001 (CAM)
  and drops port 2002 before it reaches the phone

DenmParser uses tolerant field-name matching - the Use Case API's DENM JSON
schema is not yet confirmed against real payloads.

app/src/main/res/values/strings.xml

@@ -205,7 +205,30 @@
 
     <!-- CAM Pinger — ESP32-C5-only manual bench test, equivalent to the DENM TX card above -->
     <string name="mqtt_cam_pinger_title">CAM Pinger (Manual Test)</string>
-    <string name="mqtt_cam_pinger_desc">Fixed-location 1 Hz CAM ping — verifies the serial link and ESP32 radio path without needing GNSS movement or a trip recording.</string>
+    <string name="mqtt_cam_pinger_desc">1 Hz CAM ping built from live GNSS and IMU data — verifies the serial link and ESP32 radio path without needing a trip recording.</string>
+    <string name="mqtt_cam_pinger_no_fix">Waiting for GNSS fix — nothing transmitted yet</string>
+
+    <!-- Received-CAM list (ESP32-C5 path) -->
+    <string name="v2x_cam_rx_count">%1$d station(s) in range — latest CAM per station</string>
+    <string name="v2x_cam_rx_none">No CAMs received</string>
+    <string name="v2x_cam_rx_none_hint">Decoded CAMs from nearby stations appear here as they arrive over the serial link.</string>
+    <string name="v2x_cam_rx_station">Station %1$d · %2$s</string>
+    <string name="v2x_cam_rx_kinematics">%1$.1f km/h · heading %2$.0f°</string>
+    <string name="v2x_cam_rx_distance">%1$.0f m</string>
+    <string name="v2x_cam_rx_distance_unknown">— m</string>
+
+    <!-- DENM map pins -->
+    <string name="v2x_map_denm_labeled">Hazard: cause %1$d/%2$d (station %3$d)</string>
+    <string name="v2x_map_denm_plain">Hazard from station %1$d</string>
+
+    <!-- ETSI station types -->
+    <string name="station_type_pedestrian">Pedestrian</string>
+    <string name="station_type_cyclist">Cyclist</string>
+    <string name="station_type_car">Car</string>
+    <string name="station_type_bus">Bus</string>
+    <string name="station_type_truck">Truck</string>
+    <string name="station_type_rsu">Roadside unit</string>
+    <string name="station_type_other">Type %1$d</string>
     <string name="mqtt_cam_pinger_not_connected">Connect the ESP32-C5 to enable the CAM pinger</string>
     <string name="mqtt_cam_pinger_active">Pinging — 1 CAM/s over the serial link</string>
     <string name="mqtt_cam_pinger_sent_count">Sent: %1$d</string>