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/PIL/_imagingft.pyi

@@ -0,0 +1,70 @@
+from collections.abc import Callable
+from typing import Any
+
+from . import ImageFont, _imaging
+
+class Font:
+    @property
+    def family(self) -> str | None: ...
+    @property
+    def style(self) -> str | None: ...
+    @property
+    def ascent(self) -> int: ...
+    @property
+    def descent(self) -> int: ...
+    @property
+    def height(self) -> int: ...
+    @property
+    def x_ppem(self) -> int: ...
+    @property
+    def y_ppem(self) -> int: ...
+    @property
+    def glyphs(self) -> int: ...
+    def render(
+        self,
+        string: str | bytes,
+        fill: Callable[[int, int], _imaging.ImagingCore],
+        mode: str,
+        dir: str | None,
+        features: list[str] | None,
+        lang: str | None,
+        stroke_width: float,
+        stroke_filled: bool,
+        anchor: str | None,
+        foreground_ink_long: int,
+        start: tuple[float, float],
+        /,
+    ) -> tuple[_imaging.ImagingCore, tuple[int, int]]: ...
+    def getsize(
+        self,
+        string: str | bytes | bytearray,
+        mode: str,
+        dir: str | None,
+        features: list[str] | None,
+        lang: str | None,
+        anchor: str | None,
+        /,
+    ) -> tuple[tuple[int, int], tuple[int, int]]: ...
+    def getlength(
+        self,
+        string: str | bytes,
+        mode: str,
+        dir: str | None,
+        features: list[str] | None,
+        lang: str | None,
+        /,
+    ) -> float: ...
+    def getvarnames(self) -> list[bytes]: ...
+    def getvaraxes(self) -> list[ImageFont.Axis]: ...
+    def setvarname(self, instance_index: int, /) -> None: ...
+    def setvaraxes(self, axes: list[float], /) -> None: ...
+
+def getfont(
+    filename: str | bytes,
+    size: float,
+    index: int,
+    encoding: str,
+    font_bytes: bytes,
+    layout_engine: int,
+) -> Font: ...
+def __getattr__(name: str) -> Any: ...