feat: add renaissance-oracle contract with 2-of-N multi-sig confirmation

[ComputerOracle]

feat: Oracle Contract — 2-of-N multi-sig match result verification

Adds renaissance-oracle, a dedicated on-chain oracle contract that accepts verified football match results from authorized data providers and makes them
available to the betting and rewards contracts.

What's included:

• submit_result — first oracle submits a result; enforces [started_at, finished_at] window via ledger timestamp
• confirm_result — additional oracles confirm; same oracle cannot confirm twice
• get_result / is_finalized — read-only getters for downstream contracts
• 2-of-N threshold: result is finalized only after 2 distinct oracle signatures
• Errors: OracleUnauthorized, AlreadySubmitted, AlreadyConfirmed, ResultNotFound, AlreadyFinalized, WindowViolation
• Events: ResultSub, ResultCon, ResultFin

Tests cover:

• Happy path 2-of-2 finalization
• Double-submit rejection
• Double-confirm rejection
• Late submission (after finished_at)
• Early submission (before started_at)
• Unauthorized submit and confirm

closes #12