fix(forward-log): distinguish histograms from missing-report (v1.5.3)

On machines running histogram-mode units (extensions ending in H,
e.g. H907L1R7.PG0H), every forwarded event was logging "no report"
even though histograms never get auto-exported ASCII reports from
Blastware — making the log look like every forward was misconfigured
when in fact things were working correctly.

Three log states now:

  - Waveform + paired TXT
      → "+ <txt> attached"
  - Waveform without TXT (likely BW config issue)
      → "no report ⚠"
  - Histogram (any flavour)
      → "(histogram, no report expected)"

New is_histogram_event() helper classifies by BW filename extension:
4-char ext ending in H = histogram; old-firmware 3-char extensions
default to non-histogram (safe default — we'd rather flag a missing
report than silently suppress the warning on a real waveform event).

Forwarding logic itself is unchanged — this is purely log clarity.

README.md

@@ -1,4 +1,4 @@
-# Series 3 Watcher v1.5.2
+# Series 3 Watcher v1.5.3
 
 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 (v1.5.2+)
+### SFM Event Forwarder (v1.5.3+)
 
 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.
 
@@ -155,7 +155,7 @@ To view connected watchers: **Settings → Developer → Watcher Manager**.
 
 ## Versioning
 
-Follows **Semantic Versioning**. Current release: **v1.5.2**.
+Follows **Semantic Versioning**. Current release: **v1.5.3**.
 See `CHANGELOG.md` for full history.
 
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