add first commit

example/models/counter.py

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+# src/plugins/example/models/counter.py
+from pydantic import BaseModel
+import modelvault
+
+class Counter(BaseModel):
+    # 主键字段
+    __modelvault_primary_key__ = "name"
+    # 唯一索引
+    __modelvault_indexes__ = [
+        modelvault.models.unique("name"),
+    ]
+
+    name: str          # 计数器名称（例如 "visits"）
+    value: int = 0