feat(onchain): add BatchTooLarge guard to batch_create_packages

[ifygreg01-best]

Summary

batch_create_packages had no upper bound on the number of packages per call. With gas profiling confirming calls up to N=200, an unbounded batch is a clear DoS vector on testnet.

This PR adds a configurable cap and a new error variant that fires before any allocation.

Changes

src/lib.rs

• Config.max_batch_size: u32 — new field, defaults to 100, admin-configurable up to 1000 via set_config
• Error::BatchTooLarge = 19 — new error variant
• batch_create_packages — guard added immediately after the mismatched-arrays check; returns BatchTooLarge before token validation, balance reads, or any storage write
• set_config — validates max_batch_size is in range [1, 1000]; returns Error::InvalidAmount otherwise
• init / get_config fallback — both default to max_batch_size: 100

tests/batch.rs

• Added test_batch_too_large_returns_error_and_writes_zero_rows: raises cap to 1000, submits 1001 packages with sufficient balance, asserts BatchTooLarge is returned, and confirms no package was written to storage.

All other test files

• Updated every Config { ... } literal to include max_batch_size: 100 (aid_escrow_tests.rs, boundary_validation_tests.rs, gas_profiling.rs, integration.rs).

Acceptance Criteria

• Error::BatchTooLarge returned before any allocation when batch exceeds cap
• CONTRACT_MAX_BATCH_SIZE defaults to 100, configurable to 1000 via admin
• Test asserts request for 1001 packages returns BatchTooLarge and writes zero rows
• Existing batch tests unchanged

[kilodesodiq-arch]

Hi 👋 Appreciate this PR! The CI is flagging a failing check — could you take a peek at the failed job and push a fix? Happy to help if you need a hand 🙏