feat(tholos): add set_bond_amount entrypoint and BondAmountUpdated event (#134)

[s6pa1rta3n-lab]

Description

Closes #134.

This PR introduces the set_bond_amount entrypoint to allow the contract admin to dynamically adjust the default bond required for new assertions as market conditions evolve.

Summary of Changes

• Added BondAmountUpdated event struct emitting old_bond_amount: i128 and new_bond_amount: i128.
• Implemented set_bond_amount(env: Env, new_bond_amount: i128) -> Result<(), Error> on Tholos:
  • Enforces admin authorization via admin.require_auth().
  • Rejects uninitialized contract states with Error::NotInitialized.
  • Validates 0 < new_bond_amount <= MAX_BOND_AMOUNT (returns Error::InvalidBondAmount).
  • Extends contract instance storage TTL via Self::touch_instance_ttl(&env).
  • Pause-exempt administrative function (callable while contract is paused).
  • Updates DataKey::BondAmount in instance storage.
  • Emits BondAmountUpdated event with old and new bond amounts.
• Preserves snapshotted Assertion.bond on existing in-flight assertions (dispute deposits, finalization rewards, and resolve payouts remain intact).
• Added comprehensive unit tests and proptest coverage in contracts/tholos/src/test.rs.
• Updated docs/src/CONTRACT.md with function signatures and event definitions.

Testing

• cargo fmt --check passed.
• cargo clippy --workspace --all-targets -- -D warnings passed with 0 warnings.
• cargo test passed across all workspace crates (80/80 passed).
• cargo build -p tholos --target wasm32v1-none --release succeeded.

Payout Routing

• EVM (Base/Arbitrum/Polygon/ETH): 0xF46C9F6d70C50BF81ef3588AB523a90a594a2F89
• Stellar: GCL6OXAMLD75BMTINA6EMRUDWK5THQUSHMYNLSNBCJAPZJHNYJTUNIBC

[collinsezedike]

@s6pa1rta3n-lab Closing — #134 is assigned to JohnArayaE, not you.