feat(points): add effect engines and effects shop

README.md

@@ -32,8 +32,10 @@ To Be Played is split into three repositories:
   years of full-time work, and its oldest unplayed game; most played and most loyal games; top genres and moods;
   trips to the moon, the longest gaming day, games started but under one hour; finished games per year; games per platform.
 - **Pile Points** (`/points`): points for playing games off your pile (start, finish by time to beat, 100 %, month and
-  streak bonuses; Core checks proof of play), spent in a small shop on an avatar border, a badge, a premium accent and a
-  banner frame, shown on the dashboard and the public profile. The balance is in the header.
+  streak bonuses; Core checks proof of play), spent in a small shop on an avatar border, a badge, a premium accent, a
+  banner frame, an effect for 100 % games and an animated page or banner background (CSS and SVG, in `effects.css`),
+  shown on the dashboard and the public profile. The balance is in the header. Every effect stands still with the
+  system setting "reduce motion" or the "Reduce animations" switch in the settings.
 - **Landing page**: next to the community numbers and the top games, three blocks: games per platform, top genres and
   finished games per year of all users.
 - **Library**: status filters, "short games" filter (up to 10 h), search, sorting by playtime, recently seen, newest
@@ -71,7 +73,7 @@ To Be Played is split into three repositories:
   every achievement is unlocked.
 - **Confetti**: opening a finished game plays a small confetti burst, a finished game with every achievement a big
   one; setting the status to finished plays it at once. Logo and accent colors, a canvas of our own (no library),
-  nothing with "reduce motion".
+  nothing with "reduce motion" (system or the settings switch).
 - **Finished?**: Core marks a game as finished by itself when the ending achievement is unlocked and the status was
   never set by hand. Otherwise the game page asks: "You unlocked the ending, finished?" or "You played longer than
   most players need, finished?", with "Mark as finished" and "Not yet".
@@ -85,7 +87,7 @@ To Be Played is split into three repositories:
   The owner arranges it with the same edit mode on the profile page itself (the tiles, incl. the stat groups of
   "Your stats"), and sets its look in the settings: accent, corners, banner and background from own game art
   ("Profile art" on a game's page). Visitors see the owner's look on that page only; light or dark mode stays theirs.
-- **Appearance**: accent color, corner style, wide layout, page background and banner from your own game art.
+- **Appearance**: accent color, corner style, wide layout, reduce animations, page background and banner from your own game art.
   Saved in Auth, so it follows you to every device.
 - **Language**: kept in the browser and saved in Auth; after the login Auth's language wins when one is saved. Dark
   mode stays per device. The registration sends the browser language (`de` for a German browser, else `en`): Auth