feat(master): persist scheduler tasks in RocksDB

[beinan]

Summary

• persist scheduler task records and lifecycle transitions in a master-local RocksDB with synchronous WAL writes
• reload queued tasks and requeue interrupted running tasks in FIFO order after master restart
• retain a bounded terminal task history while keeping queued and running tasks until completion
• add TASK_DB_PATH and TASK_HISTORY_LIMIT master configuration
• add a single-replica Kubernetes master Deployment with a dedicated ReadWriteOnce PVC and Recreate strategy
• install RocksDB native build dependencies in Rust CI and run master tests in the Rust test workflow

Operational notes

• the RocksDB path must be local filesystem storage backed by the master PVC, not the rollout object-store URI
• only one active master may open the PVC; the provided Deployment enforces one replica and Recreate updates
• compaction and WAL-merge operations are safe to retry when an interrupted task is recovered

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• final cargo clippy -p lance-context-master --all-targets -- -D warnings
• final cargo test -p lance-context-master --lib (22 passed)
• npm ci && npm run build (crates/lance-context-master/ui)
• parsed and validated the PVC, Service, and Deployment YAML documents