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/schema.nim

@@ -0,0 +1,67 @@
+import std/json
+
+type IntRelationTable* = object
+  ## IntRelation
+  id*: int
+
+
+type StrRelationTable* = object
+  ## StrRelation
+  uuid*: string
+
+
+type UserTable* = object
+  ## user
+  id*: string
+  name*: string
+  email*: string
+  password*: string
+  created_at*: int
+  updated_at*: int
+
+
+type AuthTable* = object
+  ## Auth
+  id*: int
+  auth*: string
+
+
+type TypesTable* = object
+  ## Types
+  id*: int
+  integer*: int
+  smallInteger*: int
+  mediumInteger*: int
+  bigInteger*: int
+  decimal*: float
+  double*: float
+  float*: float
+  uuid*: string
+  char*: string
+  string*: string
+  text*: string
+  mediumText*: string
+  longText*: string
+  date*: string
+  datetime*: string
+  time*: string
+  timestamp*: string
+  created_at*: string
+  updated_at*: string
+  deleted_at*: string
+  binary*: string
+  boolean*: bool
+  enumField*: string
+  json*: JsonNode
+  int_relation_id*: int
+  str_relation_id*: string
+
+
+type PostTable* = object
+  ## post
+  id*: string
+  title*: string
+  content*: string
+  user_id*: string
+  created_at*: int
+  updated_at*: int