feat: polling on by default and an effective-state toggle (v3.5.10)

- Background STATUS polling is enabled by default, per the spec's idle
  polling rule (TS 102 221 14.6.2): `_POLL_ENABLED = True`, __main__ runs
  `_poll_enable()` regardless of card presence (--poll-interval 0 still
  disables) and `_do_status_poll` keeps ticking while enabled even without
  a session, so a cardless start resumes as soon as a card appears.
- A new card session clears a POLLING OFF from the previous card in
  `_apply_equipped_card` before re-enabling polling.
- The Phone-tab toggle now shows the *effective* state: OFF in amber
  ("card disabled polling (POLLING OFF)") while the card suspended
  proactive polling, back to ON on the next POLL INTERVAL.  The 5 s
  background poll now passes `card_disabled` through (it was dropped, so
  an autonomously received POLLING OFF never reached the UI).
- Tests: poll_ui updated (button OFF while suspended, warning path),
  test_poll +2 (cardless ticking, module default via a subprocess check).
- Help EN/RU, docs/api.md, AGENTS; version 3.5.10; sw cache simple-v263.

573 frontend / 441 Python green.

docs/api.md

@@ -770,9 +770,12 @@ Hex, even number of digits, 1–255 bytes. Response is the same shape as
 
 ### `GET /api/poll-status`
 
-Background STATUS polling state. `card_disabled` is true after the card sent
-POLLING OFF (TS 102 223 §6.4.14): proactive polling stays suspended until a
-POLL INTERVAL arrives, independent of the operator's `enabled` switch.
+Background STATUS polling state. Polling is enabled by default (a CAT
+terminal polls during idle, TS 102 221 §14.6.2; `--poll-interval 0` disables
+it at startup) and `enabled` is the operator's switch. `card_disabled` is true
+after the card sent POLLING OFF (TS 102 223 §6.4.14): proactive polling stays
+suspended until a POLL INTERVAL arrives, independent of `enabled` - the PWA
+shows the effective state (OFF while suspended).
 
 ```json
 {"enabled": true, "interval": 30, "card_disabled": false}