Get storage at block number

[m-kus]

Summary

• Switch starknet-rs dependencies from crates.io starknet-rust-* v0.17.0 to
  m-kus/starknet-rs fork (pinned at 20b1ddeb) which adds
  StorageResponseFlag and StorageResult types
• Add optional response_flags parameter to starknet_getStorageAt per starknet-specs PR
  #370 (v0.10.1-rc.3)
• When INCLUDE_LAST_UPDATE_BLOCK is passed, the response becomes {"value": "0x...", "last_update_block": N} instead of a plain felt — the block number is found by scanning state
  diffs in reverse
• Without the flag, behavior is unchanged (returns plain felt)

Motivation

The discovery service needs to know which block last modified a storage slot to efficiently
traverse transaction history backwards. This avoids scanning every block sequentially.

Changes

File	What
Cargo.toml	starknet-rs deps → git fork
emitted_event.rs	Compat: default transaction_index/event_index to 0 (fields absent in
upstream starknet-rs)
endpoints_ws.rs	Compat: default commitment/count fields for origin block headers
models/mod.rs	response_flags: Option<Vec<StorageResponseFlag>> on GetStorageInput
json_rpc_response.rs	StorageResult variant on StarknetResponse
starknet/mod.rs	find_last_storage_update_block() — reverse scan of num_to_hash +
hash_to_state_diff
json_rpc_handler.rs	Pass response_flags through dispatch
endpoints.rs	Branch on flag: return StorageResult or Felt

Test plan

• cargo check — compiles cleanly
• cargo test -p starknet-devnet-server — 70 tests pass (includes new deserialization tests
  for response_flags)
• cargo test -p starknet-devnet-core — 116 tests pass
• Integration test: deploy contract → write storage → call with/without flags → verify
  response
• Manual: start devnet, send tx, curl starknet_getStorageAt with response_flags: ["INCLUDE_LAST_UPDATE_BLOCK"]