feat(phase1): add image storage utilities

- Create backend/services/image_storage.py with 4 core functions:
  - sanitize_filename(): remove unsafe chars, limit to 255 chars, convert to lowercase
  - get_unique_filename(): handle collisions with UUID suffix (format: {name}_{uuid8}_{variant}.jpg)
  - ensure_image_directories(): create /images/ root and category subdirs on startup
  - save_image(): save bytes to /images/{category}/{filename}, returns relative path
- Create comprehensive test suite (22 tests) covering all functionality
- Integrate ensure_image_directories() into FastAPI startup event
- Directory structure: /images/{category}/{filename}
- Collision handling: auto-suffix with UUID if filename exists
- All tests passing, pathlib.Path for safe operations

venv/lib/python3.12/site-packages/anthropic/pagination.py

@@ -0,0 +1,182 @@
+# File generated from our OpenAPI spec by Stainless. See CONTRIBUTING.md for details.
+
+from typing import List, Generic, TypeVar, Optional
+from typing_extensions import override
+
+from ._base_client import BasePage, PageInfo, BaseSyncPage, BaseAsyncPage
+
+__all__ = ["SyncPage", "AsyncPage", "SyncTokenPage", "AsyncTokenPage", "SyncPageCursor", "AsyncPageCursor"]
+
+_T = TypeVar("_T")
+
+
+class SyncPage(BaseSyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    has_more: Optional[bool] = None
+    first_id: Optional[str] = None
+    last_id: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def has_next_page(self) -> bool:
+        has_more = self.has_more
+        if has_more is not None and has_more is False:
+            return False
+
+        return super().has_next_page()
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        if self._options.params.get("before_id"):
+            first_id = self.first_id
+            if not first_id:
+                return None
+
+            return PageInfo(params={"before_id": first_id})
+
+        last_id = self.last_id
+        if not last_id:
+            return None
+
+        return PageInfo(params={"after_id": last_id})
+
+
+class AsyncPage(BaseAsyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    has_more: Optional[bool] = None
+    first_id: Optional[str] = None
+    last_id: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def has_next_page(self) -> bool:
+        has_more = self.has_more
+        if has_more is not None and has_more is False:
+            return False
+
+        return super().has_next_page()
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        if self._options.params.get("before_id"):
+            first_id = self.first_id
+            if not first_id:
+                return None
+
+            return PageInfo(params={"before_id": first_id})
+
+        last_id = self.last_id
+        if not last_id:
+            return None
+
+        return PageInfo(params={"after_id": last_id})
+
+
+class SyncTokenPage(BaseSyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    has_more: Optional[bool] = None
+    next_page: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def has_next_page(self) -> bool:
+        has_more = self.has_more
+        if has_more is not None and has_more is False:
+            return False
+
+        return super().has_next_page()
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        next_page = self.next_page
+        if not next_page:
+            return None
+
+        return PageInfo(params={"page_token": next_page})
+
+
+class AsyncTokenPage(BaseAsyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    has_more: Optional[bool] = None
+    next_page: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def has_next_page(self) -> bool:
+        has_more = self.has_more
+        if has_more is not None and has_more is False:
+            return False
+
+        return super().has_next_page()
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        next_page = self.next_page
+        if not next_page:
+            return None
+
+        return PageInfo(params={"page_token": next_page})
+
+
+class SyncPageCursor(BaseSyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    next_page: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        next_page = self.next_page
+        if not next_page:
+            return None
+
+        return PageInfo(params={"page": next_page})
+
+
+class AsyncPageCursor(BaseAsyncPage[_T], BasePage[_T], Generic[_T]):
+    data: List[_T]
+    next_page: Optional[str] = None
+
+    @override
+    def _get_page_items(self) -> List[_T]:
+        data = self.data
+        if not data:
+            return []
+        return data
+
+    @override
+    def next_page_info(self) -> Optional[PageInfo]:
+        next_page = self.next_page
+        if not next_page:
+            return None
+
+        return PageInfo(params={"page": next_page})