Add svxdr: the live-data backend (nodelist + proxy; astmeta/xlink optional), config example, systemd unit, INSTALL section 9

svxdr sources from the internal repo with AGPL headers; install/svxdr.json.example is a plain-reflector
layout (reflector 8099 -> proxy 8090 -> nodelist 8098) with CHANGEME secrets and no site values.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

INSTALL.md

@@ -230,32 +230,80 @@ Answer the prompts (callsign, e-mail, password, admin level). Levels:
 
 Log in on the web page with that callsign. The **Admin** menu appears.
 
-## 9. Live data API — what this repository does NOT contain
+## 9. Live data backend: svxdr
 
 The dashboard (node list, map, monitor, last-heard, trunks) fetches JSON and
 Server-Sent Events from `/svxportal/api/...`, which nginx proxies to
-`127.0.0.1:8098`. That backend service is **not included** here. Without it
-the account/admin/talkgroup pages work, but the front page's node list, map,
-monitor, last-heard and trunks views simply stay **empty**. There is no error
-banner: the API helper returns null on a failed fetch and the page keeps its
-empty tables. Check the browser console (404 on `/svxportal/api/status`) if
-you are unsure.
+`127.0.0.1:8098`. That backend is **svxdr**, included in `svxdr/`: one Go
+binary with four modules switched on or off per box in `/etc/svxlink/svxdr.json`.
 
-Endpoints the UI expects:
+| Module | What it does | A plain reflector needs it? |
+|--------|--------------|-----------------------------|
+| `proxy` | reads the reflector's own `/status`, caches it, serves it enriched on 8090 | yes |
+| `nodelist` | builds the node/lastheard/monitor/trunk data from the proxy + Redis, serves `/api/*` on 8098 | yes |
+| `astmeta` | AllStar/Asterisk AMI talker metadata for USRP bridges | no, leave `false` |
+| `xlink` | relays talker events to an MQTT broker | no, leave `false` |
+
+Without svxdr the account/admin/talkgroup pages work, but the front page's
+live views stay **empty** with no error banner (404 on `/svxportal/api/status`
+in the browser console).
+
+### Build
+
+```bash
+sudo apt install golang-go          # Go 1.24 or newer
+cd svxdr && CGO_ENABLED=0 go build -trimpath -o svxdr . && cd ..
+sudo install -m0755 svxdr/svxdr /usr/local/bin/svxdr
+```
+
+### Configure
+
+```bash
+sudo cp install/svxdr.json.example /etc/svxlink/svxdr.json
+sudo chmod 640 /etc/svxlink/svxdr.json
+sudoedit /etc/svxlink/svxdr.json
+```
+
+Set at least:
+
+- `redis.socket` and `redis.password` -> the same Redis as `auth/config.php` (step 3).
+- `proxy.reflector_status_url` -> your reflector's `HTTP_SRV_PORT` status URL.
+  With `HTTP_SRV_PORT=8099` in `svxreflector.conf` (as in
+  `install/svxreflector.conf.example`) the default `http://127.0.0.1:8099/status` is right.
+- `nodelist.reflector_status_url` stays on the proxy (`http://127.0.0.1:8090/status`).
+- All `CHANGEME` tokens: any random string; the ingest tokens only matter if a
+  remote box posts talker metadata to you.
+- `nodelist.federation.seeds`: `/status` URLs of other reflectors you want in the
+  map that your own trunks do not reach. Empty = only what the crawl finds.
+  `aggregate_url` empty disables the gap detector.
+
+The port layout must match the nginx config: reflector 8099 -> proxy 8090 ->
+nodelist 8098 -> nginx `/svxportal/api/`.
+
+### Run
+
+```bash
+sudo cp install/systemd/svxdr.service /etc/systemd/system/svxdr.service
+sudo systemctl daemon-reload
+sudo systemctl enable --now svxdr
+systemctl status svxdr --no-pager
+curl -s http://127.0.0.1:8098/healthz          # -> ok
+curl -s http://127.0.0.1:8098/api/status | head -c 300
+```
+
+Config changes are picked up with `sudo systemctl reload svxdr` (SIGHUP), no
+restart needed. `journalctl -u svxdr -f` shows what it polls and serves.
+
+Endpoints the UI uses:
 
 | Path | Used by |
 |------|---------|
-| `/svxportal/api/status` | node table, topology |
+| `/svxportal/api/status` | node table, topology, CTCSS |
 | `/svxportal/api/stream` | live updates (SSE) |
 | `/svxportal/api/lastheard` | last-heard list |
 | `/svxportal/api/monitor-nodes` | monitor view |
 | `/svxportal/api/local-trunks` | trunks view |
 
-You need to provide something that serves these, for example a small service
-that reads your reflector's `HTTP_SRV_PORT` status endpoint
-([GeuReflector](https://github.com/audric/GeuReflector) serves `/status` there)
-and republishes it. The static reflector status page in `help.html` describes the fields.
-
 ## 10. Reflector admin features (optional, need sudo helpers)
 
 The pages **Admin → Reflector**, **Certificates**, **Node control** and **MQTT**