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/api-websocket.md

@@ -0,0 +1,120 @@
+# WebSocket API
+
+Full-duplex streaming for real-time data feeds and push notifications.
+
+## Connection
+
+```
+ws://localhost:8081/ws
+```
+
+## Client Example
+
+```javascript
+const ws = new WebSocket('ws://localhost:8081/ws');
+
+ws.onopen = () => {
+  console.log('Connected');
+  ws.send(JSON.stringify({
+    type: 'query',
+    sql: 'SELECT * FROM users'
+  }));
+};
+
+ws.onmessage = (event) => {
+  const data = JSON.parse(event.data);
+  console.log('Received:', data);
+};
+```
+
+## Message Format
+
+```json
+{
+  "type": "query",
+  "id": "uuid",
+  "sql": "SELECT * FROM users"
+}
+```
+
+## Message Types
+
+### Query Request
+
+```json
+{
+  "type": "query",
+  "id": "123",
+  "sql": "SELECT * FROM users"
+}
+```
+
+### Query Response
+
+```json
+{
+  "type": "result",
+  "id": "123",
+  "data": [
+    {"id": 1, "name": "Alice"},
+    {"id": 2, "name": "Bob"}
+  ]
+}
+```
+
+### Error Response
+
+```json
+{
+  "type": "error",
+  "id": "123",
+  "error": {
+    "code": "INVALID_QUERY",
+    "message": "Syntax error"
+  }
+}
+```
+
+### Subscription
+
+Subscribe to changes:
+
+```json
+{
+  "type": "subscribe",
+  "id": "sub1",
+  "table": "users"
+}
+```
+
+### Push Notification
+
+Server push:
+
+```json
+{
+  "type": "push",
+  "table": "users",
+  "action": "insert",
+  "data": {"id": 3, "name": "Charlie"}
+}
+```
+
+## JavaScript Client
+
+```javascript
+class BaraDBClient {
+  constructor(url) {
+    this.ws = new WebSocket(url);
+    this.pending = new Map();
+  }
+
+  query(sql) {
+    return new Promise((resolve, reject) => {
+      const id = crypto.randomUUID();
+      this.pending.set(id, { resolve, reject });
+      this.ws.send(JSON.stringify({ type: 'query', id, sql }));
+    });
+  }
+}
+```