docs: add commit refs for BUG-17/18

BUGS.md

@@ -30,7 +30,7 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
 
 ### BUG-18 — Pi needs offline timekeeping (no RTC)
 - **Status**: `CLOSED` 2026-08-14
-- **Commit**: `PENDING`
+- **Commit**: `bf4f3d3`
 - **Fix**: DS3231 RTC module installed on the free I²C bus (SDA pin 3, SCL pin 5, 3.3V pin 1,
   GND pin 6) with a CR2032 (charge diode removed). Pi config: `dtparam=i2c_arm=on` +
   `dtoverlay=i2c-rtc,ds3231` in `/boot/firmware/config.txt`, `i2c-tools` installed,
@@ -44,7 +44,7 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
 
 ### BUG-17 — Server trip timestamps wrong after an offline period
 - **Status**: `CLOSED` 2026-08-14
-- **Commit**: `PENDING`
+- **Commit**: `bf4f3d3`
 - **Fix**: root cause was BUG-18 — no RTC, so offline the Pi ran on a stale `fake-hwclock`
   time and NTP snapped the clock forward mid-trip. Fixed by installing the DS3231 (BUG-18).
 - **Verification**: RTC power-cycle test passed (BUG-18). Historical trips 25136/25137 keep