feat: Archiv-Backfill, responsive Bilder und Site-Meta

Ergänzt Backfill- und Hilfsskripte, erzeugt nach der Pixazo-Generierung
komprimierte srcset-Varianten, validiert leere Bilder und fügt Favicon,
Web Manifest sowie Open-Graph-/Twitter-Tags in die Templates ein.

Co-authored-by: Cursor <cursoragent@cursor.com>

generator/images.py

@@ -0,0 +1,90 @@
+"""Responsive JPEG variants for hero images."""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+from PIL import Image
+
+VARIANT_WIDTHS = (360, 560, 800)
+JPEG_QUALITY = 82
+DATE_IMAGE_RE = re.compile(r"^(\d{4}-\d{2}-\d{2})\.jpg$")
+
+
+def image_public_path(date_iso: str, width: int | None = None) -> str:
+    if width is None:
+        return f"/img/{date_iso}.jpg"
+    return f"/img/{date_iso}-{width}w.jpg"
+
+
+def build_srcset(date_iso: str, widths: list[int], full_width: int) -> str:
+    parts = [f"{image_public_path(date_iso, w)} {w}w" for w in widths]
+    parts.append(f"{image_public_path(date_iso)} {full_width}w")
+    return ", ".join(parts)
+
+
+def create_responsive_variants(img_dir: Path, date_iso: str) -> dict[str, str] | None:
+    source = img_dir / f"{date_iso}.jpg"
+    if not source.exists():
+        return None
+
+    with Image.open(source) as im:
+        im = im.convert("RGB")
+        full_width, full_height = im.size
+        generated: list[int] = []
+
+        for width in VARIANT_WIDTHS:
+            if width >= full_width:
+                continue
+            height = round(full_height * width / full_width)
+            resized = im.resize((width, height), Image.Resampling.LANCZOS)
+            out = img_dir / f"{date_iso}-{width}w.jpg"
+            resized.save(out, "JPEG", quality=JPEG_QUALITY, optimize=True)
+            generated.append(width)
+
+        im.save(source, "JPEG", quality=JPEG_QUALITY, optimize=True)
+
+    srcset = build_srcset(date_iso, generated, full_width)
+    default_src = image_public_path(date_iso, 560) if 560 in generated else image_public_path(date_iso)
+    thumb_src = image_public_path(date_iso, 360) if 360 in generated else image_public_path(date_iso)
+
+    return {
+        "src": default_src,
+        "srcset": srcset,
+        "sizes": "(max-width: 768px) 100vw, 560px",
+        "og": image_public_path(date_iso),
+        "thumb_src": thumb_src,
+        "thumb_srcset": srcset,
+        "thumb_sizes": "(max-width: 640px) 50vw, 360px",
+    }
+
+
+def load_image_descriptor(img_dir: Path, date_iso: str) -> dict[str, str] | None:
+    if not (img_dir / f"{date_iso}.jpg").exists():
+        return None
+    if not (img_dir / f"{date_iso}-360w.jpg").exists():
+        return create_responsive_variants(img_dir, date_iso)
+    widths = [w for w in VARIANT_WIDTHS if (img_dir / f"{date_iso}-{w}w.jpg").exists()]
+    with Image.open(img_dir / f"{date_iso}.jpg") as im:
+        full_width = im.size[0]
+    srcset = build_srcset(date_iso, widths, full_width)
+    return {
+        "src": image_public_path(date_iso, 560) if 560 in widths else image_public_path(date_iso),
+        "srcset": srcset,
+        "sizes": "(max-width: 768px) 100vw, 560px",
+        "og": image_public_path(date_iso),
+        "thumb_src": image_public_path(date_iso, 360) if 360 in widths else image_public_path(date_iso),
+        "thumb_srcset": srcset,
+        "thumb_sizes": "(max-width: 640px) 50vw, 360px",
+    }
+
+
+def iter_source_images(img_dir: Path) -> list[Path]:
+    if not img_dir.exists():
+        return []
+    sources = []
+    for path in sorted(img_dir.glob("*.jpg")):
+        if DATE_IMAGE_RE.match(path.name):
+            sources.append(path)
+    return sources