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/setup.nim

@@ -0,0 +1,51 @@
+import
+  std/strformat,
+  std/json,
+  std/asyncdispatch,
+  ../src/allographer/query_builder,
+  ../src/allographer/schema_builder
+
+from ./connections import rdb
+
+template bench*(msg, body) =
+  block:
+    echo "=== " & msg
+    let start = cpuTime()
+    body
+    echo cpuTime() - start
+
+proc setup*() =
+  rdb.create(
+    table("auth",[
+      Column.increments("id"),
+      Column.string("auth")
+    ]),
+    table("user",[
+      Column.increments("id"),
+      Column.string("name").nullable(),
+      Column.string("email").nullable(),
+      Column.foreign("auth_id").reference("id").onTable("auth").onDelete(SET_NULL)
+    ])
+  )
+
+  # seeder
+  seeder(rdb, "auth"):
+    rdb.table("auth").insert(@[
+      %*{"auth": "admin"},
+      %*{"auth": "user"}
+    ])
+    .waitFor
+
+  seeder(rdb, "user"):
+    var user: seq[JsonNode]
+    for i in 1..10:
+      let authId = if i mod 2 == 0: 2 else: 1
+      user.add(
+        %*{
+          "name": &"user{i}",
+          "email": &"user{i}@mail.com",
+          "auth_id": authId
+        }
+      )
+
+    rdb.table("user").insert(user).waitFor