Decode standard PPS sub-types + RST CLK extension → ATR data rate

- capture.py: map GSMTAP PPS request/response (0x02/0x03) to 'pps',
  matching the pcap-import mapping (was decoded as TPDU live)
- decode.py: parse the optional RST CLK extension (sigrok v1.9.0+,
  payload flag bit 0); ATR gains clk_hz/data_rate/etu_us derived from
  TA1 Fi/Di (data_rate = clk_hz × D / F)
- database.py: CLK state is consumed by the next ATR (no stale rate
  for an ATR without preceding RST); a late-arriving RST measurement
  is backfilled onto the ATR it belongs to; replay context carries
  the CLK across pagination/live polling
- PWA: ATR detail shows CLK/Data rate/ETU; RST event detail shows CLK
- tests: PPS mapping, CLK parse with/without flag, rate math,
  DB consume + backfill round-trips
- README/RUS updated
- Bump 1.22.18, SW cache v49->v50

README.md

@@ -130,14 +130,20 @@ tunable via `--log-interval SECONDS`.
 The GSMTAP listener also accepts the **sigrok-iso7816-stream** decoder
 (https://github.com/anttro/sigrok_iso7816_stream) — an FX2-logic-analyzer
 passive SIM sniffer that emits the same GSMTAP-SIM format on UDP 4729. Its
-custom sub-types for RST/VCC line events (`0x10`/`0x11`, added for
+standard PPS request/response sub-types (`0x02`/`0x03`) are decoded as PPS,
+and its custom sub-types for RST/VCC line events (`0x10`/`0x11`, added for
 compatibility with that project) are decoded as `RESET ASSERTED/DE-ASSERTED`
 and `VCC ON/OFF` timeline markers, and a reset-assert or power-removal
-correctly invalidates the file-selection tracking. GSMTAP packets carrying
-the `GSMTAP_FLAG_BAD_FCS` desync flag (set by that decoder on mis-framed
-exchanges) are surfaced as a flagged/desynced entry in the capture timeline,
-so such artefacts are easy to spot when reviewing a capture rather than
-silently altering the decode.
+correctly invalidates the file-selection tracking. When an RST event carries
+the measured CLK frequency (decoder v1.9.0+, optional payload extension), the
+following ATR is annotated with the CLK frequency, data rate and ETU derived
+from its TA1 Fi/Di (`data_rate = clk_hz × D / F`); the measurement is
+consumed by the ATR so a later ATR without a reset gets no stale rate (a
+late-arriving measurement is backfilled onto the ATR it belongs to). GSMTAP
+packets carrying the `GSMTAP_FLAG_BAD_FCS` desync flag (set by that decoder
+on mis-framed exchanges) are surfaced as a flagged/desynced entry in the
+capture timeline, so such artefacts are easy to spot when reviewing a capture
+rather than silently altering the decode.
 
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