feat: add expire_match with configurable ledger timeout to unblock stuck funds

[Sundriveauto]

Closes #281

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Problem

If player1 creates a match and deposits but player2 never deposits, player1's funds are locked indefinitely with no way to reclaim them.

Changes

types.rs

• Added DataKey::MatchTimeout variant for storing a configurable timeout value

errors.rs

• Added Error::MatchNotExpired = 12 returned when expire_match is called too early

lib.rs

• Added DEFAULT_MATCH_TIMEOUT_LEDGERS = 17_280 (~24 hours at 5s/ledger)
• Added expire_match(match_id): callable by anyone once env.ledger().sequence() - m.created_ledger >= timeout. Refunds any deposited stakes and transitions the match to Cancelled. Timeout is read from DataKey::MatchTimeout with fallback to the default constant.

tests.rs

• test_expire_match_refunds_depositor_after_timeout: verifies player1 gets their stake back after the timeout elapses
• test_expire_match_fails_before_timeout: verifies Error::MatchNotExpired is returned if called too early

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