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

.gitignore

@@ -0,0 +1,15 @@
+# Build
+build/
+nimcache/
+nimblecache/
+
+# Temp
+*.tmp
+*.log
+
+# Data
+data/
+
+# OS
+.DS_Store
+Thumbs.db