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/database/migrations/create_all_type_table.nim

@@ -0,0 +1,42 @@
+import std/json
+import ../../../src/allographer/schema_builder
+import ../connection
+
+proc createAllTypeTable*() =
+  ## 0002
+  rdb.create([
+    table("IntRelation", [
+      Column.increments("id")
+    ]),
+    table("StrRelation", [
+      Column.uuid("uuid")
+    ]),
+    table("Types", [
+      Column.increments("id"),
+      Column.integer("integer"),
+      Column.smallInteger("smallInteger"),
+      Column.mediumInteger("mediumInteger"),
+      Column.bigInteger("bigInteger"),
+      Column.decimal("decimal", 10, 3),
+      Column.double("double", 10, 3),
+      Column.float("float"),
+      Column.uuid("uuid"),
+      Column.char("char", 255),
+      Column.string("string"),
+      Column.text("text"),
+      Column.mediumText("mediumText"),
+      Column.longText("longText"),
+      Column.date("date"),
+      Column.datetime("datetime"),
+      Column.time("time"),
+      Column.timestamp("timestamp"),
+      Column.timestamps(),
+      Column.softDelete(),
+      Column.binary("binary"),
+      Column.boolean("boolean"),
+      Column.enumField("enumField", ["A", "B", "C"]),
+      Column.json("json"),
+      Column.foreign("int_relation_id").reference("id").onTable("IntRelation").onDelete(SET_NULL),
+      Column.strForeign("str_relation_id").reference("uuid").onTable("StrRelation").onDelete(SET_NULL)
+    ]),
+  ])

clients/nim-allographer/example/database/migrations/init_databaase.nim

@@ -0,0 +1,23 @@
+import ../../../src/allographer/schema_builder
+import ../connection
+
+proc initDatabaase*() =
+  ## 0001
+  rdb.create([
+    table("user", [
+      Column.uuid("id").index().comment("User ID"),
+      Column.string("name").comment("User name"),
+      Column.string("email").comment("User email address"),
+      Column.string("password").comment("User password"),
+      Column.integer("created_at").index().comment("Created at"),
+      Column.integer("updated_at").index().comment("Updated at"),
+    ], "User table"),
+    table("post", [
+      Column.uuid("id").index().comment("Post ID"),
+      Column.string("title").comment("Post title"),
+      Column.string("content").comment("Post content"),
+      Column.strForeign("user_id").reference("id").onTable("user").comment("User ID"),
+      Column.integer("created_at").index().comment("Created at"),
+      Column.integer("updated_at").index().comment("Updated at"),
+    ], "Post table"),
+  ])

clients/nim-allographer/example/database/migrations/migrate.nim

@@ -0,0 +1,12 @@
+import std/asyncdispatch
+import ../../../src/allographer/schema_builder
+import ../connection
+import ./init_databaase
+import ./create_all_type_table
+
+proc migrate*() =
+  initDatabaase()
+  createAllTypeTable()
+
+migrate()
+createSchema(rdb).waitFor()