feat: standardize escrow contract event schema and topics

[Chrisbankz0]

#closes
#318
Summary
Standardized escrow contract event emission so backend indexers can consume a strict, consistent topic schema.

What changed
events.rs

Added a dedicated escrow event schema module.
Defined a fixed primary topic: Escrow.
Standardized secondary event types:
Initialized
Funded
Released
Reclaimed
DisputeInitiated
DisputeResolved
Cleanup
Added structured payload types for each event.
lib.rs
Rewired all env.events().publish(...) calls to use the new standardized topics tuple:
(Escrow, , engagement_id)
Replaced legacy local event definitions with imports from the new events.rs module.
README.md

Documented the escrow event schema and topics for backend developers and indexers.

Why
Provides a consistent event namespace for all escrow lifecycle events.
Makes on-chain event consumption easier and more reliable for the FastAPI backend or other indexer services.
Reduces event handling ambiguity and supports a standardized contract event contract.
Testing
Recommended commands:

cd contracts
cargo test -p escrow
cargo build --release --target wasm32-unknown-unknown
Note: In the current editor environment, cargo was not available on the terminal PATH, so tests were not executed here.

Files changed
events.rs
lib.rs
README.md

#closes

[ohamamarachi474-del]

@Chrisbankz0 please look in to ci fail and after wards ill review

[Chrisbankz0]

i've resolved it

[ohamamarachi474-del]

@Chrisbankz0