v3.32.1: "Start counter value" in the outfile import

The import created presets with the store's default counter (1).  Cards
whose counters are already past it had to be edited preset by preset
afterwards.

- The outfile preview form gains a "Start counter value" field (default
  1, the store's value).  The value is written into every created keyset
  of every imported card - parse_outfile's `start_counter`, 1-10 hex
  digits, whitespace stripped and uppercased; a bad value raises and the
  endpoint answers 400.  Without it the store's default still applies
  (the field is omitted), so the API keeps its old behaviour.
- The preview shows the counter; an import stores the protocol's
  10-digit form (counter_hex).
- Docs: api.md (the field), help EN/RU (the form).
- Version strings + the PWA cache bumped together (simple-v459).

Tests: the parser (every keyset, normalisation, unset, the bad values),
the endpoint (the preview's keysets, the 400, the stored padded form),
the PWA (the field's default, the controls' normalisation, both bodies).
1008 Python + 953 frontend green.

docs/api.md

@@ -351,6 +351,10 @@ into a preview.
 - `tar_keyset` — an optional **global default keyset** (1–15) for the TAR
   entries that do not name one (the API's shorthand; the PWA sends per-row
   keysets instead).
+- `start_counter` — the counter **every created keyset starts from** (1–10 hex
+  digits; whitespace stripped, uppercased).  Without it the store's default
+  (`1`) applies.  A bad value is a `400`; the import stores the protocol's
+  10-digit form.
 
 Recognised columns (case-insensitive): `ICCID` (the digits + odd-nibble F
 pad, the plain digits, spaced digits or the raw nibble-swapped EF hex all