Colmi rings never showed the Vitals "Measure" button: it was gated on
BLOOD_PRESSURE/BLOOD_SUGAR (the Jring combined 0x23 packet), which Colmi
hardware doesn't have. Colmi did already support on-demand HR (0x69) but
only exposed it via the coach tool, and had no live SpO2 path at all.

Add live SpO2 via the real-time command family, then surface a spot
measurement (HR + SpO2) both as a Vitals button and automatically on
connect.

- ColmiEncoder/Protocol: live SpO2 start ([0x69, reading_type=3, START])
  and stop ([0x6A, 3, 0, 0]), per the colmi_r02_client real-time protocol.
- ColmiDecoder: branch the 0x69 real-time response on reading_type so
  type 3 decodes to Spo2Result (value at v[3]); the HR path is unchanged.
- ColmiSyncEngine: startSpO2/stopSpO2 now drive the live spot command
  (historical big-data SpO2 sync is untouched). Add MANUAL_SPO2 capability.
- RingSyncCoordinator: measureSpot() runs HR then SpO2, capability-gated;
  autoMeasureOnConnect() fires it ~2s after connect. Wired into onConnected.
- Vitals screen: show the Measure button for rings with manual HR/SpO2
  (spot mode) alongside the existing combined flow, with its own countdown
  and "measuring heart rate & SpO2" copy.

Verified on a Pixel 8 with an R10: auto-measure on connect populated HR
and SpO2 (96%), the value confirmed against the ring's raw 0x69/3 frame,
and the manual Measure button runs the spot flow.

Builds on the R10 pairing fix + measurement feature with the support,
observability, and correctness work needed to ship it.

Self-update (release-only):
- In-app updater polls the GitHub latest release, compares versionCode from
  the `v<name>+<code>` tag, downloads + installs the universal APK. On-launch
  (throttled) + a Settings "Check for updates" button.
- Tag-driven GitHub Actions workflow builds, signs, and attaches the APKs.
- Coexisting `.debug` build (applicationIdSuffix) so a debug install never
  wipes the release app's data; enable buildConfig; env-overridable signing.

Diagnostics + privacy:
- Harden the export: own-PID logcat capture + a crash handler (new Application)
  persisting stack traces, plus accurate build/version info.
- PHI scrubbing on by default (health values, ring serial, MAC addresses
  removed; models/opcodes/control frames/errors kept) with an opt-out toggle
  for full unmasked BLE frames. Verified masked vs full on-device.

Ring removal (restores the iOS two-action model):
- "Forget" is now non-destructive (unbind + disconnect only) for both rings —
  no more power-off/factory-reset wiping a Colmi's history on a normal remove.
- New Colmi-only "Factory Reset" syncs latest history first, then resets,
  behind a confirmation dialog.

Fixes:
- Persist + prettify the connected ring's name (was always showing the default
  "SMART_RING"; now "Colmi R10"); shared ringModelLabel.
- Live-activity (0x73 0x12) decode read big-endian fields as little-endian,
  inflating steps to millions and locking a garbage daily total via max-merge.
  Decode big-endian + plausibility guard + self-heal of a stuck total.
- Drop autoMeasureOnConnect: connecting no longer pins the optical sensor on.
  Matches iOS — connect runs the history sync only; vitals come from the ring's
  periodic monitoring + the manual Measure button.

End users get diagnostics from the in-app export, so there's no need to
distribute a debug APK. The debug variant stays for local dev/repro
(adb, run-as, system-Bluetooth logs); it's just no longer a release asset.

Two reasons the Colmi green LED kept pulsing after a measurement:

- The HR stop frame was wrong: manualHeartRate(false) sent [0x69, 0x02],
  but 0x69 is CMD_START_REAL_TIME — so the 'stop' actually started another
  real-time reading and the sensor never switched off (the ring only timed
  out on its own). Send CMD_STOP_REAL_TIME (0x6A) instead, mirroring SpO2.

- measureHR/measureSpO2/measureCombined sent the stop after the wait loop,
  not in a finally. The Measure button runs in the screen's coroutine scope,
  so navigating away mid-measurement cancelled it before the stop ran. Wrap
  each in try/finally so the sensor is always switched off.