Workout mode: HR-only recording (зарядка) without GPS

New 'Зарядка' activity type records a session with no GPS - no location
service, no watchPosition, no track points - just the heart-rate poll and a
timer, for indoor exercise. kcal comes from HR (Keytel gross minus BMR, net
like the rest of the app) and counts in the daily balance.

- gps.js: GPS.hrKcalNet; startRecording/stopRecording 'workout' branches;
  the HR poll appends [relSec,bpm] samples.
- db.js: gps_sessions.hr_samples column + setSessionHrSamples.
- main.js: 'Зарядка (пульс)' option; renderWorkoutInline (map-less live
  screen: big HR, timer, kcal, connect-sensor button); renderWorkoutDetail
  (HR chart by zones, load, avg/max).
- tools/hr_log.py: background HR logger (standard 0x180D, no pairing).

Sensor read from the desktop confirmed on a Coospo H808S (F7:72:74:A4:FB:07,
~1 Hz) without pairing.

tools/hr_log.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+"""Фоновый логгер ЧСС с BLE HR-датчика (стандарт 0x180D / 0x2A37, напр. Coospo H808S).
+Пишет строки 'epoch,bpm' в указанный файл, пока процесс не убьют. Авто-переподключение
+при обрыве. Спаривание не требуется.
+
+Использование: python3 tools/hr_log.py <BLE-addr> <logfile>
+"""
+import asyncio, sys, time
+from bleak import BleakClient, BleakScanner
+
+ADDR = sys.argv[1]
+LOG = sys.argv[2]
+HR_CHR = "00002a37-0000-1000-8000-00805f9b34fb"
+
+
+def make_cb(logf):
+    def cb(_, data: bytearray):
+        flags = data[0]
+        bpm = int.from_bytes(data[1:3], "little") if flags & 1 else data[1]
+        logf.write(f"{time.time():.1f},{bpm}\n")
+        logf.flush()
+    return cb
+
+
+async def main():
+    logf = open(LOG, "a")
+    logf.write(f"# {time.time():.1f} start addr={ADDR}\n")
+    logf.flush()
+    while True:
+        try:
+            dev = await BleakScanner.find_device_by_address(ADDR, timeout=15.0)
+            if dev is None:
+                logf.write(f"# {time.time():.1f} not_found, retry\n")
+                logf.flush()
+                await asyncio.sleep(3)
+                continue
+            async with BleakClient(dev) as cli:
+                logf.write(f"# {time.time():.1f} connected\n")
+                logf.flush()
+                await cli.start_notify(HR_CHR, make_cb(logf))
+                while cli.is_connected:
+                    await asyncio.sleep(1)
+            logf.write(f"# {time.time():.1f} disconnected, reconnect\n")
+            logf.flush()
+        except Exception as e:
+            logf.write(f"# {time.time():.1f} err {e}\n")
+            logf.flush()
+            await asyncio.sleep(3)
+
+
+asyncio.run(main())