refactor: split catchup state into dedicated store

[vietddude]

Summary

Refactor catchup processing to use a dedicated Redis-backed catchupstore instead of storing catchup state in the block store.

What changed

• Split catchup state out of pkg/store/blockstore into pkg/store/catchupstore
• Updated worker wiring to inject and use catchupStore where catchup progress is loaded and persisted
• Simplified CatchupWorker so it only reads existing catchup ranges and processes them
• Kept catchup behavior aligned with the regular worker’s responsibility for creating new ranges
• Added/updated tests for:
  • catchup worker behavior
  • factory wiring
  • catchup store persistence and range merging

Behavior changes

• Catchup progress is now stored and loaded from Redis
• Catchup worker no longer owns range creation logic
• Catchup state is isolated from the main block store, which reduces coupling and makes recovery/persistence cleaner

Catchup status source

Catchup progress is now sourced directly from Redis via catchupStore.

• CatchupWorker loads catchup ranges from Redis
• /status refreshes catchup ranges from Redis before returning the snapshot
• catchup state no longer depends on other workers to materialize or update the ranges