feat(settings): an Animations section in App Settings

Every animation setting now has its own App Settings section, right after
Appearance (owner: easier to find). It holds the Entrance Theme (the former
Entrance Animations row), Tile Animations, and an Open lab button that closes
settings and opens the per-surface lab (?animlab=1). Appearance keeps the skin,
identity and tab settings. New animation settings go in this section;
test/app-settings-structure.test.ts pins it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/styles.css

@@ -20081,8 +20081,8 @@ body.tile-grid-resizing--row * {
 }
 
 /* ── Tile grid entrance styles (entrance-animations.js TILE_ANIM_STYLES) ───
-   Picked by the Entrance Animations theme (App Settings → Appearance) or per
-   surface in the lab (?animlab=1); `settle` is the rule above, the default,
+   Picked in App Settings → Animations (Tile Animations, or preset by the
+   Entrance Theme) or per surface in the lab (?animlab=1); `settle` is the rule above, the default,
    and what a reload restores with. Any other style is held one frame
    (.tile--enter-hold: invisible, not animating) while the entrance module
    orders the cascade and measures the tile's source on the final layout, then