chore(release): v0.31.0 — report parity + the inverted rescue

Cuts Unreleased to v0.31.0 and writes the theme now that the whole release is
visible, per the convention adopted today.

Two threads landed. Blastware Event/FFT-Report parity — the FFT, the USBM
RI8507 compliance chart, and the sensor self-check decoded for both series and
standardized into the .h5 (schema v2, /sensor_check). And the ach_server rescue
flags out of the BE12599 field emergency, which invert the wedged-unit recovery:
answer the unit's call instead of racing a Stop into the gaps between its
dial-outs.

Version stamped in pyproject.toml, CLAUDE.md and README.md. TOOL_VERSION was
already at 0.31.0 — it came in with the sensor-check work, and it is what makes
the backfill pick up the new /sensor_check group without --force.

⚠ This release owes prod a backfill: .h5 schema v1 -> v2, ~2 h on the NAS.
Stated in the Migration block.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qcu9ByJfuKBQxmrWb8rSrN

README.md

@@ -1,4 +1,4 @@
-# seismo-relay  `v0.30.0`
+# seismo-relay  `v0.31.0`
 
 A ground-up replacement for **Blastware** — Instantel's aging Windows-only
 software for managing seismographs.  Supports both the **MiniMate Plus