feat: rename to Drucken, 86 image sizes, fix the distorted crop editor

The crop frame had width:100% together with max-height, so the height was
clamped while the width stayed - the frame lost the target aspect ratio and
object-fit:fill stretched the picture into it. Measured at 390px: frame 0.843
instead of 0.778, picture 8.3% too wide. The width now follows from the allowed
height and the ratio, and the image carries its own aspect-ratio instead of a
second percentage, so it cannot stretch at all.

Dragging was fine but felt dead: at fill zoom the crop sits at the stop in one
axis. The editor now states which way it can move, double-tap zooms, arrow keys
nudge, and the zoom slider shows its factor.

Sizes: 41 -> 86 in ten groups, including US inch sizes, instant-film picture
areas, cards, DIN A0-A7 and eleven aspect ratios as physical sizes.

The tab is called Drucken now; /druck and /passbilder redirect there.

src/pages/druck.astro

@@ -1,4 +1,4 @@
 ---
-// Alte Adresse — die Funktion heißt jetzt „Passbilder".
-return Astro.redirect('/passbilder', 301);
+// Alte Adresse — die Funktion heißt jetzt „Drucken".
+return Astro.redirect('/drucken', 301);
 ---