Vault: withdraw event parity with `EVENT_SCHEMA.md`

[greatest0fallt1me]

Description

Emit withdraw / withdraw_to events with topics/data exactly as documented; add tests where possible.

Requirements and context

• Fix drift between docs and implementation.
• Ensure owner-only auth remains intact.

Suggested execution

• Fork the repo and create a branch: git checkout -b feature/vault-withdraw-events
• Implement changes in the Callora-Contracts Soroban workspace (contracts/*/src/).
• Run cargo fmt, cargo clippy --all-targets --all-features -- -D warnings, and cargo test from the workspace root.
• For WASM release builds: cargo build --target wasm32-unknown-unknown --release -p callora-vault (adjust -p if the crate name differs).

Deliverables

• lib.rs + test.rs + EVENT_SCHEMA.md.

Test and commit

• Run tests and ./scripts/coverage.sh (or cargo tarpaulin per tarpaulin.toml).
• Cover edge cases; include summarized test output and brief security notes in the PR description.

Example commit message

feat(vault): withdraw event parity with schema

Guidelines

• Minimum 95% line coverage for touched crates (workspace policy).
• Clear documentation (Rust /// on public items where applicable; repo markdown as needed).
• Timeframe: 96 hours from assignment unless agreed otherwise.

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[Ebuka321]

@Ebuka321 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hello Good day. please can i work on these ?

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