fix(flaunch): exact Permit2 amountIn and short deadline

[SashaMIT]

Flaunch sellCoin was signing a Permit2 AllowanceTransfer for maxUint160 with a ~10-year expiration and sigDeadline whenever the current allowance was too low. That leaves the UniversalRouter with unbounded, long-lived rights to the memecoin after (or instead of) the intended sell.

This permits only the sell amountIn for 30 minutes. Same over-approval hygiene as the CDP exact Permit2 path in #1409, different provider and Permit2 surface (local typed data on Flaunch, not ERC-20 approve to Permit2). Sibling of #1409/#1410/#1411. Does not reopen those PRs' findings.

Test plan

• pnpm exec jest --testPathPattern='flaunch/flaunchActionProvider' --coverage=false (20/20)
• Regression: typed-data amount equals amountIn and is not maxUint160
• Regression: expiration/sigDeadline are 30 minutes (not multi-year)
• Regression: sufficient existing allowance skips signTypedData

Made with Cursor

[cb-heimdall]

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[SashaMIT]

Consolidating our open queue to reduce triage load. Closing this for now; the core set we are keeping open is #1392, #1404, #1405, #1409, #1421, #1423. Happy to reopen or refile this specific fix if a maintainer wants it.