feat: complete Phase 3 + new production roadmap for Web/ERP

- Thread-safety: locks in LSMTree and Graph engines
- Raft network transport: async TCP, serialization, heartbeat, 3-node election test
- CI/CD: GitHub Actions workflow
- Cleanup: remove dead code, unused imports, build artifacts
- New PLAN.md targeting production Web/ERP readiness
- 216 tests passing

src/barabadb/core/crossmodal.nim

@@ -2,7 +2,6 @@
 import std/tables
 import std/os
 import std/sequtils
-import ../core/types
 import ../storage/lsm
 import ../vector/engine as vengine
 import ../graph/engine as gengine