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/seeder/data/user_seeder.nim

@@ -0,0 +1,24 @@
+import std/json
+import std/strformat
+import std/asyncdispatch
+import std/oids
+import std/times
+import ../../../../src/allographer/query_builder
+import ../../connection
+import ../../schema
+
+proc userSeeder*() {.async.} =
+  seeder(rdb, "user"):
+    var userList: seq[JsonNode]
+    for i in 1..10:
+      let row = UserTable(
+        id: $genOid(),
+        name: &"user {i}",
+        email: &"user{i}@example.com",
+        password: &"password{i}",
+        created_at: now().toTime().toUnix().int,
+        updated_at: now().toTime().toUnix().int,
+      )
+      userList.add(%row)
+
+    rdb.table("user").insert(userList).await