fix: support FA2 token swaps (LIVE-36514)

[dbaranov-hoodies]

Checklist

• [ x] App update process has been followed
• [ x] Target branch is develop
• [ x] Application version has been bumped

Swapping USDT (Tezos) failed: the app answered 0x6985 to the final signature
and Ledger Live showed "Operation denied on device".

swap_check_validity() only understood a native XTZ transfer. A token swap
signs an FA2 transfer call, so the operation carries 0 mutez and its
destination is the token contract, while the recipient and the amount live in
the Michelson parameters — both comparisons could never match.

The check now branches on whether Exchange passed a coin configuration:

• native XTZ: unchanged
• token: requires 0 mutez, exactly one fully decoded transfer, the called
  contract and token id to resolve in the FA2 registry, that entry's symbol
  and decimals to match the Ledger-signed coin configuration, and the
  Michelson to_ and amount to match the swap's destination and amount

swap_handle_get_printable_amount() now uses the token's ticker and decimals
instead of hardcoded XTZ/6, so the Exchange screen no longer labels a USDt
amount as XTZ.

The parser keeps the decoded recipient, token id and amount in the operation
state, since the emit steps reuse both the CAPTURE and decimal buffers and the
frame holding the token id is popped before validation runs. Anything it
cannot represent leaves the transfer unvalidated, so the swap refuses while
the display path is untouched.

Unit tests now build with -DHAVE_SWAP; two new ones pin the captured operation
and check that a Micheline fallback leaves the swap fields unset.

Version bumped to 3.2.4 (3.2.3 is released but its tags are not ancestors of
develop, so that number is taken).

Needs the app-exchange tests in LedgerHQ/app-exchange#382, and a CAL entry
publishing ticker + decimals for FA2 tokens on Tezos — Exchange forwards only
the sub-coin config to the coin app, so without it the app is never told which
token the operation moves and keeps refusing, by design.

[github-actions]

Code coverage report

Per-file coverage

Package	Line Rate	Branch Rate	Health
app.src.parser	85%	61%	✔
Summary	85% (1501 / 1770)	61% (758 / 1244)	✔