fix: resize gallery thumbnails for current high density cards

tests/test_gallery_thumbnail.py

@@ -0,0 +1,28 @@
+import io
+
+from PIL import Image
+
+
+def test_gallery_thumbnail_upgrades_existing_cache_and_reuses_it(client, settings):
+    cache = settings.data_dir / "cache"
+    original = cache / "living-room-1.original"
+    thumb = cache / "living-room-1-thumb.jpg"
+    Image.new("RGB", (1600, 1200), "blue").save(original, "JPEG")
+    Image.new("RGB", (300, 225), "blue").save(thumb, "JPEG")
+    url = "/api/v1/devices/living-room/images/1/file?thumbnail=true"
+    result = client.get(url)
+    assert result.status_code == 200
+    assert Image.open(io.BytesIO(result.content)).size == (860, 645)
+    modified = thumb.stat().st_mtime_ns
+    assert client.get(url).content == result.content
+    assert thumb.stat().st_mtime_ns == modified
+    assert len(list(cache.glob("living-room-1-thumb*"))) == 1
+    assert Image.open(original).size == (1600, 1200)
+
+
+def test_gallery_thumbnail_does_not_upscale_small_source(client, settings):
+    original = settings.data_dir / "cache" / "living-room-1.original"
+    Image.new("RGBA", (200, 400), (255, 0, 0, 255)).save(original, "PNG")
+    result = client.get("/api/v1/devices/living-room/images/1/file?thumbnail=true")
+    assert result.status_code == 200
+    assert Image.open(io.BytesIO(result.content)).size == (200, 400)