feat: wire protocol integration in TCP server

- Server now reads binary wire protocol messages (header + payload)
- Implements recvExact for reliable message framing
- Query execution against LSM-Tree for SELECT/INSERT/DELETE
- SELECT supports point reads (WHERE key = 'value') and full scans
- INSERT parses simple EdgeDB-style syntax
- DELETE with WHERE clause
- Wire protocol responses: Data, Complete, Error, Pong
- Export wire protocol read/write helpers for external use
- Add scanMemTable to LSMTree for full scans
- Add GEL/ to .gitignore
- All 214 tests pass

src/barabadb/storage/lsm.nim

@@ -403,3 +403,11 @@ proc close*(db: var LSMTree) =
 proc memTableSize*(db: LSMTree): int = db.memTable.len
 proc sstableCount*(db: LSMTree): int = db.sstables.len
 proc dir*(db: LSMTree): string = db.dir
+
+proc scanMemTable*(db: LSMTree): seq[Entry] =
+  ## Return all entries from memory (memTable + immutableMem)
+  result = @[]
+  for e in db.memTable.entries:
+    result.add(e)
+  for e in db.immutableMem.entries:
+    result.add(e)