fix(settings): add SFM Forward tab to settings dialog (v1.5.1)

v1.5.0 shipped the forwarder module + INI keys but the settings
dialog wasn't extended, so the only way operators could enable
forwarding was hand-editing config.ini.  This adds a sixth tab
("SFM Forward") with:

  - Forward events to SFM    checkbox
  - SFM Server URL           entry + Test button (GETs /health)
  - Forward Interval (sec)   spinbox
  - Quiescence (sec)         spinbox
  - Missing-Report Grace     spinbox
  - HTTP Timeout             spinbox
  - State File               entry + Browse...

Save-time guard: enabling the forwarder without a URL raises a
validation error rather than silently saving a non-functional
config.

Patch release — same on-disk INI schema, no config migration.

README.md

@@ -1,4 +1,4 @@
-# Series 3 Watcher v1.5.0
+# Series 3 Watcher v1.5.1
 
 Monitors Instantel **Series 3 (Minimate)** call-in activity on a Blastware server. Runs as a **system tray app** that starts automatically on login, reports heartbeats to terra-view, and self-updates from Gitea.
 
@@ -88,7 +88,7 @@ All settings live in `config.ini`. The Setup Wizard covers every field, but here
 | `UPDATE_SOURCE` | `gitea` (default) or `url` — where to check for updates |
 | `UPDATE_URL` | Base URL of the update server when `UPDATE_SOURCE = url` (e.g. terra-view URL). The watcher fetches `/api/updates/series3-watcher/version.txt` and `/api/updates/series3-watcher/series3-watcher.exe` from this base. |
 
-### SFM Event Forwarder (v1.5.0+)
+### SFM Event Forwarder (v1.5.1+)
 
 Forwards each Blastware event binary (and its paired `<binary>.TXT` ASCII report when present) to an SFM server's `/db/import/blastware_file` endpoint, where the report is parsed and the rich per-channel stats (PPV, ZC Freq, Time of Peak, Peak Acceleration / Displacement, sensor self-check) land in a searchable database. **Default-off** — existing deployments keep their old behaviour after auto-updating until the operator opts in.
 
@@ -137,7 +137,7 @@ To view connected watchers: **Settings → Developer → Watcher Manager**.
 
 ## Versioning
 
-Follows **Semantic Versioning**. Current release: **v1.5.0**.
+Follows **Semantic Versioning**. Current release: **v1.5.1**.
 See `CHANGELOG.md` for full history.
 
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