net: re-address hub network 10.60.1.0/24 -> 192.168.8.0/24

The project was designed around a 10.60.1.0/24 travel-router network,
but the actual RemoteRig router uses 192.168.8.0/24 (the C6 associates
and gets 192.168.8.x; hub confirmed at 192.168.8.56). Replace the
network prefix everywhere (last octet preserved; GoPro 10.5.5.1 left
alone).

- scripts/setup-pi.sh: static IP 192.168.8.56/24, gateway 192.168.8.1,
  deploy/health command examples updated
- esp32-mqtt-bridge.cpp: default mqtt_broker -> 192.168.8.56
- firmware/data/config.json: broker -> 192.168.8.56 (wifi_password kept
  blank in git; real value flashed to the device only)
- docs (CONTEXT, MQTT_CONTRACT, READMEs, wireframes): gateway/hub/DHCP
  and example IPs re-addressed for consistency

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/MQTT_CONTRACT.md

@@ -7,7 +7,7 @@
 
 ```
                    ┌──────────────────────────────────┐
-                   │     Travel Router (10.60.1.1)   │
+                   │     Travel Router (192.168.8.1)   │
                    │         DHCP: .100-.200            │
                    └──────┬──────────┬──────────┬──────┘
                           │          │          │
@@ -15,7 +15,7 @@
           ▼                          ▼                          ▼
    ┌──────────────┐         ┌──────────────┐         ┌──────────────┐
    │   ESP32 #1   │         │   ESP32 #2   │         │  Pi Zero 2 W │
-   │  10.60.1.101 │        │  10.60.1.102 │        │ 10.60.1.56  │
+   │  192.168.8.101 │        │  192.168.8.102 │        │ 192.168.8.56  │
    │ STA→Router   │        │ STA→Router   │        │ Mosquitto    │
    │ MQTT relay   │        │ MQTT relay   │        │ Go backend   │
    └──────┬───────┘        └──────┬───────┘        │ React UI     │
@@ -32,14 +32,14 @@
    └──────────────┘        └──────────────┘
 ```
 
-- **Travel router:** Self-contained, no internet. Gateway `10.60.1.1`. DHCP pool: `10.60.1.100-200`
-- **Pi Zero 2 W:** Static IP `10.60.1.56`. Runs Mosquitto (port 1883), Go backend (port 8080), serves React UI
+- **Travel router:** Self-contained, no internet. Gateway `192.168.8.1`. DHCP pool: `192.168.8.100-200`
+- **Pi Zero 2 W:** Static IP `192.168.8.56`. Runs Mosquitto (port 1883), Go backend (port 8080), serves React UI
 - **ESP32s:** DHCP from router. Each stays on the travel-router LAN, relays MQTT to/from its paired ESP8266 over UART
-- **User device:** Connects to router, opens `http://10.60.1.56:8080` for dashboard
+- **User device:** Connects to router, opens `http://192.168.8.56:8080` for dashboard
 
 ## MQTT Broker
 
-- **Host:** `10.60.1.56` (Pi Zero 2 W)
+- **Host:** `192.168.8.56` (Pi Zero 2 W)
 - **Port:** `1883` (default MQTT, no TLS — closed network)
 - **Auth:** None (closed network, no external access)
 - **Client ID format:** `remoterig-<esp32_mac_last6>` (e.g., `remoterig-a1b2c3`)
@@ -222,7 +222,7 @@ Hub health status broadcast.
 ESP32 boots
   │
   ├── Connects to travel router Wi-Fi
-  ├── Connects to MQTT broker (10.60.1.56:1883)
+  ├── Connects to MQTT broker (192.168.8.56:1883)
   ├── Publishes announce (retained) on cameras/<id>/announce
   │
   ▼
@@ -275,6 +275,6 @@ When ESP32 loses connection to travel router:
 
 ## Open Questions
 
-1. **NTP/time sync:** How do ESP32s get accurate time without internet? Options: (a) Pi runs NTP server, (b) ESP32 queries Pi's HTTP /api/v1/time endpoint, (c) GPS module. **Recommendation:** Pi runs NTPd, ESP32s use SNTP from `10.60.1.56`.
+1. **NTP/time sync:** How do ESP32s get accurate time without internet? Options: (a) Pi runs NTP server, (b) ESP32 queries Pi's HTTP /api/v1/time endpoint, (c) GPS module. **Recommendation:** Pi runs NTPd, ESP32s use SNTP from `192.168.8.56`.
 2. **Camera naming:** Should `friendly_name` be configurable from dashboard after auto-registration? **Recommendation:** Yes — allow rename via UI, stored in cameras table.
 3. **Firmware OTA:** Should ESP32 firmware updates be possible over this network? **Recommendation:** Yes but out of scope for MVP.