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/sarrogate_key.nim

@@ -0,0 +1,55 @@
+import std/asyncdispatch
+import std/strformat
+import std/json
+import ../src/allographer/query_builder
+import ../src/allographer/schema_builder
+from ./connections import rdb
+
+
+rdb.create([
+  table("auth",[
+    Column.increments("id"),
+    Column.string("name")
+  ]),
+  table("users",[
+    Column.increments("user_id"),
+    Column.string("name").nullable(),
+    Column.string("email").nullable(),
+    Column.string("password").nullable(),
+    Column.string("address").nullable(),
+    Column.date("birth_date").nullable(),
+    Column.foreign("auth_id").reference("id").onTable("auth").onDelete(SET_NULL)
+  ])
+])
+
+# シーダー
+seeder rdb, "auth":
+  rdb.table("auth").insert(@[
+    %*{"name": "admin"},
+    %*{"name": "user"}
+  ])
+  .waitFor
+
+let total = 20
+var insertData: seq[JsonNode]
+for i in 1..total:
+  let authId = if i mod 2 == 0: 1 else: 2
+  insertData.add(
+    %*{
+      "name": &"user{i}",
+      "email": &"user{i}@gmail.com",
+      "password": &"password{i}",
+      "auth_id": authId
+    }
+  )
+
+rdb.table("users").insert(insertData).waitFor()
+echo rdb.table("users").get().waitFor()
+
+echo rdb.table("users").find(2, key="user_id").waitFor()
+echo rdb.table("auth").find(1).waitFor()
+
+rdb.table("users").delete(2, key="user_id").waitFor()
+rdb.table("auth").delete(2).waitFor()
+echo rdb.table("users").limit(3).get().waitFor()
+echo rdb.table("auth").limit(3).get().waitFor()