feat: initial BaraDB — multimodal database engine in Nim

- LSM-Tree storage engine with WAL, bloom filter, MemTable
- BaraQL query language: lexer (80+ tokens), recursive descent parser, AST
- Vector engine: HNSW + IVF-PQ indexes, 4 distance metrics
- Graph engine: adjacency list, BFS/DFS, Dijkstra, PageRank
- Full-Text Search: inverted index, BM25 ranking, stemming, stop words
- Type system: 17 types (int/float/string/uuid/json/vector/...)
- Async TCP server
- 21 passing tests

src/baradadb.nim

@@ -0,0 +1,15 @@
+## BaraDB — Multimodal Database Engine
+## Main entry point
+import std/asyncdispatch
+import barabadb/core/server
+import barabadb/core/config
+
+proc main() =
+  let config = loadConfig()
+  echo "BaraDB v0.1.0 — Multimodal Database Engine"
+  echo "Listening on ", config.address, ":", config.port
+  var server = newServer(config)
+  waitFor server.run()
+
+when isMainModule:
+  main()