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/protocol.md

@@ -0,0 +1,99 @@
+# Protocol Reference
+
+BaraDB supports multiple protocols for client communication.
+
+## Binary Wire Protocol
+
+Efficient big-endian binary protocol:
+
+```nim
+import barabadb/protocol/wire
+
+# Query message
+let msg = makeQueryMessage(1, "SELECT * FROM users")
+
+# Ready message
+let ready = makeReadyMessage(1)
+
+# Error message
+let error = makeErrorMessage(1, 42, "Syntax error")
+```
+
+### Message Types
+
+| Type | ID | Description |
+|------|-----|-------------|
+| Query | 0x01 | Execute query |
+| Insert | 0x02 | Insert data |
+| Update | 0x03 | Update data |
+| Delete | 0x04 | Delete data |
+| Ready | 0x05 | Ready for next command |
+| Error | 0x06 | Error response |
+| Auth | 0x07 | Authentication |
+| Batch | 0x08 | Batch operations |
+
+## HTTP/REST API
+
+JSON-based REST API:
+
+```nim
+import barabadb/protocol/http
+
+var router = newHttpRouter(port = 8080)
+
+router.get("/api/users", proc(req: Request): Future[JsonNode] {.async.} =
+  return %*[{"id": 1, "name": "Alice"}])
+
+router.post("/api/users", proc(req: Request): Future[JsonNode] {.async.} =
+  return %*{"status": "created"})
+```
+
+## WebSocket API
+
+Full-duplex streaming:
+
+```nim
+import barabadb/core/websocket
+
+var server = newWsServer(port = 8081)
+server.onMessage = proc(ws: WebSocket, data: seq[byte]) {.gcsafe.} =
+  echo "Received: ", cast[string](data)
+asyncCheck server.run()
+```
+
+## Authentication
+
+JWT-based authentication:
+
+```nim
+import barabadb/protocol/auth
+
+var am = newAuthManager("secret-key")
+let token = am.createToken(JWTClaims(sub: "user1", role: "admin"))
+let result = am.validateCredentials(AuthCredentials(authMethod: amToken, payload: token))
+```
+
+## Rate Limiting
+
+Token bucket rate limiting:
+
+```nim
+import barabadb/protocol/ratelimit
+
+var rl = newRateLimiter(rlaTokenBucket, globalRate = 1000, perClientRate = 100)
+if rl.allowRequest("client-123"):
+  echo "Request allowed"
+```
+
+## Connection Pooling
+
+```nim
+import barabadb/protocol/pool
+
+var pool = newConnectionPool(
+  minConnections = 5,
+  maxConnections = 100
+)
+let conn = pool.acquire()
+pool.release(conn)
+```