restructure: move backend into backend/

backend/app/pagination.py

@@ -0,0 +1,30 @@
+from typing import Generic, TypeVar
+
+from fastapi import Query
+from pydantic import BaseModel
+
+from .config import get_settings
+
+T = TypeVar("T")
+
+
+class Page(BaseModel, Generic[T]):
+    total: int
+    limit: int
+    offset: int
+    items: list[T]
+
+
+class PageParams:
+    """Reusable dependency for `?limit=&offset=` with env-configured caps."""
+
+    def __init__(
+        self,
+        limit: int = Query(default=None, ge=1, description="Max rows to return"),
+        offset: int = Query(default=0, ge=0, description="Rows to skip"),
+    ):
+        settings = get_settings()
+        if limit is None:
+            limit = settings.default_limit
+        self.limit = min(limit, settings.max_limit)
+        self.offset = offset