feat(clients): add nim-allographer client with BaraDB driver support

- Pure Nim wire protocol client (async + sync, no C FFI)
- Query Builder: fluent API, SQL generator, execution, transactions
- Schema Builder: create/alter/drop tables, column operations
- Connection pool with aging and timeout handling
- ORM integration via compile-time DB_BARADB switch
- Tests: test_open, test_query
- Documentation: README.md, PLAN_BARADB.md

clients/nim-allographer/example/prepare.nim

@@ -0,0 +1,33 @@
+import std/asyncdispatch
+import std/json
+import std/random
+import std/times
+import ../src/allographer/query_builder
+import ../src/allographer/schema_builder
+import ../src/allographer/query_builder/libs/sqlite/sqlite_impl
+from connections import rdb
+
+randomize()
+
+rdb.create(
+  table("num_table", [
+    Column.integer("id"),
+    Column.integer("randomnumber")
+  ])
+)
+
+seeder rdb, "num_table":
+  var data = newSeq[JsonNode]()
+  for i in 1..10000:
+    data.add(%*{"id": i, "randomnumber": rand(10000)})
+  rdb.table("num_table").insert(data).waitFor
+
+let start = cpuTime()
+(proc(){.async.}=
+  let conn = rdb.pools.conns[0].conn
+  let stmt = await conn.prepare("select * from num_table where id = ?", 30)
+  let resultSet = await conn.preparedQuery(@["1"], stmt)
+  echo resultSet[0]
+)()
+.waitFor
+echo cpuTime() - start