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.

installer.iss

@@ -3,7 +3,7 @@
 
 [Setup]
 AppName=Series 3 Watcher
-AppVersion=1.4.4
+AppVersion=1.5.0
 AppPublisher=Terra-Mechanics Inc.
 DefaultDirName={pf}\Series3Watcher
 DefaultGroupName=Series 3 Watcher