Add comprehensive documentation with i18n support (EN/BG)

- Add docs/ folder with English (en/) and Bulgarian (bg/) documentation
- Create index.md with language switching and links
- English docs: installation, quickstart, architecture, baraql, storage,
  schema, lsm, btree, vector, graph, fts, columnar, transactions,
  distributed, protocol, udf, api-binary, api-http, api-websocket
- Bulgarian docs: installation, quickstart, architecture, baraql,
  schema, lsm, btree, vector, graph, fts, transactions, distributed
- Update README license to BSD 3-Clause
- Add LICENSE file with BSD 3-Clause text

docs/en/graph.md

@@ -0,0 +1,52 @@
+# Graph Engine
+
+Adjacency list storage with built-in algorithms for graph traversal and analysis.
+
+## Usage
+
+```nim
+import barabadb/graph/engine
+
+var g = newGraph()
+let alice = g.addNode("Person", {"name": "Alice"}.toTable)
+let bob = g.addNode("Person", {"name": "Bob"}.toTable)
+discard g.addEdge(alice, bob, "knows")
+
+# Traversal
+let bfs = g.bfs(alice)
+let dfs = g.dfs(alice)
+let path = g.shortestPath(alice, bob)
+let ranks = g.pageRank()
+```
+
+## Algorithms
+
+| Algorithm | Description |
+|-----------|-------------|
+| `bfs` | Breadth-first traversal |
+| `dfs` | Depth-first traversal |
+| `dijkstra` | Shortest weighted path |
+| `pageRank` | Node importance ranking |
+| `louvain` | Community detection |
+| `patternMatch` | Subgraph isomorphism |
+
+## Cypher Query
+
+```nim
+import barabadb/graph/cypher
+
+var engine = newCypherEngine(g)
+let results = engine.execute("""
+  MATCH (p:Person)-[:KNOWS]->(friend:Person)
+  WHERE p.name = 'Alice'
+  RETURN friend.name
+""")
+```
+
+## Pattern Matching
+
+```sql
+MATCH (a:Person)-[:KNOWS]->(b:Person)-[:KNOWS]->(c:Person)
+WHERE a.name = 'Alice'
+RETURN b.name, c.name
+```