feat(contracts): add structured contract events with indexed topics

[Chigybillionz]

feat(contracts): structured contract events with indexed topics across escrow, reputation & loyalty

Summary

Adds a complete event layer to all three core contracts. Every state-changing entry point now emits exactly one typed event with indexable topics, enabling the on-chain ingestion pipeline (#22) to filter by appointment, worker, or client without scanning every ledger. Failed operations emit nothing.

Issue

Closes #45 

Root Cause

None of the three contracts published events on state changes, making contract state invisible off-chain and blocking the ingestion pipeline.
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Solution Implemented

Added  #[contractevent]  structs with topic annotations to each contract, emitting via  .publish(&env)  after all state mutations. Topics use a two-symbol prefix ( contract/action ) followed by  #[topic]  fields for indexed filtering. Data uses  Map<Symbol, Val>  format for stable field names.
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Key Changes

- 16 new event types across 3 contracts with deterministic topic ordering
- SEP-41-compatible  Transfer  and  Burn  events on loyalty-token
- Full event catalogue documented in contracts README with indexer filtering examples
- Comprehensive event tests including adversarial (no-event-on-failure) assertions

Affected Files

-  contracts/escrow/src/lib.rs  — 11 event structs + publish calls
-  contracts/reputation/src/lib.rs  — 1 event struct + publish call
-  contracts/loyalty-token/src/lib.rs  — 4 event structs + publish calls
-  contracts/escrow/src/test.rs  — event assertions
-  contracts/reputation/src/test.rs  — event assertions
-  contracts/loyalty-token/src/test.rs  — event assertions
-  README.md  — event catalogue documentation
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Trade-offs / Considerations

-  approve  does not emit an event — SEP-41 does not define one, and adding it would deviate from standard tooling expectations
- CI cargo caching was already in place ( Swatinem/rust-cache@v2  in  .github/workflows/soroban-ci.yml ), so no changes needed
- The WASM target is  wasm32v1-none  (not  wasm32-unknown-unknown ) per Soroban SDK requirements on Rust 1.82+

Testing

-  cargo fmt --check  — pass
-  cargo clippy --workspace -- -D warnings  — pass
-  cargo test --workspace  — 286/286 pass
-  cargo build --workspace --target wasm32v1-none --release  — pass
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CI Verification

All CI-equivalent local checks pass. The repository's  .github/workflows/soroban-ci.yml  runs  cargo fmt --check ,  cargo clippy -- -D warnings ,  cargo test , and  soroban contract build  — all validated locally.
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Please verify my work

[Chigybillionz]

please comfirm this my branch