feat: canonical Nim client refactor with typed rows, pool, and allographer wrapper

- Extract wire protocol into clients/nim/src/baradb/wire.nim
- Add BaraError exception hierarchy
- Refactor BaraClient/SyncClient with typedRows, AsyncLock request queue, timeouts, TLS config
- Add BaraPool and optional HTTP fallback
- Add mock-server wire and pool unit tests
- Bump baradb nimble package to 1.2.0
- Make nim-allographer depend on canonical baradb client
- Use typed rows in allographer toJson
- Deprecate src/barabadb/client/client.nim
- Update docs/en/clients.md and clients/nim/README.md

clients/nim/baradb.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "1.1.6"
+version       = "1.2.0"
 author        = "BaraDB Team"
 description   = "Official Nim client for BaraDB — async binary protocol client"
 license       = "Apache-2.0"