feat(tholos): add set_admin rotation path and AdminUpdated event (#128)

[s6pa1rta3n-lab]

Summary

Closes #128.

This PR implements an admin rotation / recovery mechanism for the tholos contract:

• Added set_admin(env: Env, new_admin: Address) -> Result<(), Error> to allow the current admin to rotate the admin key.
• Enforces authorization with admin.require_auth().
• Updates instance storage TTL via Self::touch_instance_ttl(&env).
• Defines and publishes the AdminUpdated { old_admin, new_admin } contract event.
• Marked pause-exempt (similar to update_resolvers) so that admin recovery is possible during an active emergency incident.
• Added comprehensive unit and TTL tests in contracts/tholos/src/test.rs.
• Updated docs/src/CONTRACT.md documentation for functions and events.

Verification

• cargo fmt --check passes cleanly.
• cargo clippy --workspace --all-targets -- -D warnings passes with 0 warnings.
• cargo test passes 100% across all workspace crates (60 tholos unit/proptests + 43 tholos-v2 tests + 43 asserter-consumer tests + 26 demo-consumer tests).

Payout Routing

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

[collinsezedike]

@s6pa1rta3n-lab Closing — #128 is assigned to dimin4241-svg, not you.