feat(forward): SFM event forwarder (v1.5.0)

When SFM_FORWARD_ENABLED=true and SFM_URL is set, every Blastware
event binary in the ACH watch folder is forwarded to an SFM server's
/db/import/blastware_file endpoint as a multipart POST.  The paired
<binary>.TXT ASCII report (which Blastware's ACH writes alongside
each event) is shipped in the same request, letting the SFM server
index the full per-channel stats — PPV, ZC Freq, Time of Peak, Peak
Acceleration / Displacement, Peak Vector Sum + time, sensor
self-check Pass/Fail per channel, and monitor-log timestamps —
without depending on the still-undecoded BW waveform body codec.

New module event_forwarder.py:
  - is_event_binary() filename matcher (BW's <P><serial3><stem>.<ext>
    scheme; rejects .MLG, .TXT, .log, .ini, .h5, etc.)
  - ForwardState (.json file keyed by sha256 — idempotent across
    restarts and auto-updates)
  - find_pending_events() with quiescence + grace-period guards
  - Hand-rolled multipart encoder (stdlib-only)
  - forward_event_pair() / forward_pending() — POST loop with
    structured per-event outcomes

Wired into series3_watcher.run_watcher() on its own cadence
(SFM_FORWARD_INTERVAL_SECONDS, default 60s) so it doesn't slow the
existing 5-min heartbeat scan.

Default-off: existing 1.4.x deployments keep their old behaviour
after auto-updating until an operator sets SFM_URL +
SFM_FORWARD_ENABLED=true and restarts.

17 unit tests in test_event_forwarder.py cover filename matching,
state idempotency, scan logic (quiescence, grace, max age,
already-forwarded, .TXT pairing), multipart byte shape, and an
end-to-end POST against a tiny stdlib http.server fake.

Bumps version 1.4.4 → 1.5.0 (minor — additive feature, no API break).
Requires SFM server v0.16+ for the paired-.TXT import endpoint.

README.md

@@ -1,4 +1,4 @@
-# Series 3 Watcher v1.4.4
+# Series 3 Watcher v1.5.0
 
 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.
 
@@ -88,6 +88,22 @@ 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+)
+
+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.
+
+| Key | Description |
+|-----|-------------|
+| `SFM_FORWARD_ENABLED` | `true` to enable forwarding (default `false`) |
+| `SFM_URL` | Base URL of the SFM server, e.g. `http://10.0.0.44:8200` |
+| `SFM_FORWARD_INTERVAL_SECONDS` | Scan-and-forward cadence (default `60`); independent of the heartbeat interval |
+| `SFM_QUIESCENCE_SECONDS` | Skip files modified within this many seconds (default `5`) — avoids forwarding mid-write |
+| `SFM_MISSING_REPORT_GRACE_SECONDS` | If a `.TXT` partner hasn't appeared after this many seconds, forward the binary alone (default `60`) |
+| `SFM_HTTP_TIMEOUT` | Per-request HTTP timeout in seconds (default `60`) |
+| `SFM_STATE_FILE` | Path to the JSON state file tracking sha256 of forwarded events. Leave blank to default to `<log dir>/sfm_forwarded.json` |
+
+Forwarded files are tracked by sha256 in the state file, so re-scans / restarts / auto-updates never re-POST the same content. A failed POST stays in the pending pool and is retried on the next interval.
+
 ---
 
 ## Tray Icon
@@ -121,7 +137,7 @@ To view connected watchers: **Settings → Developer → Watcher Manager**.
 
 ## Versioning
 
-Follows **Semantic Versioning**. Current release: **v1.4.4**.
+Follows **Semantic Versioning**. Current release: **v1.5.0**.
 See `CHANGELOG.md` for full history.
 
 ---