Drop the pearls currency

Pearls were earned every run and spent on nothing: the aquarium fills up by
finishing worlds, not by paying for it. A counter that only ever goes up is one
more stat competing for attention on the result sheet and the home screen, and
one more field to carry through the run payload, the progress file and both test
suites.

Stars and the animal ladder already say how a run went, so nothing is lost.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/components/TippenApp.tsx

@@ -291,7 +291,6 @@ export function TippenApp({ onExit }: Props) {
         compact={screen === "run"}
         status={
           <div style={{ display: "flex", gap: 12, alignItems: "center", color: "var(--paper)", fontWeight: 800 }}>
-            <span>🦪 {progress.pearls}</span>
             {!progress.settings.sound && <span title="Ton aus">🔇</span>}
           </div>
         }

web/src/components/tippen/AppHeader.tsx

@@ -5,7 +5,7 @@ import type { ReactNode } from "react";
 
 interface Props {
   title?: string;
-  /** Shown on the right - pearls, streak, a back hint. */
+  /** Shown on the right - streak, best animal, a back hint. */
   status?: ReactNode;
   /** Smaller header while a lesson is running, so the target line gets the room. */
   compact?: boolean;

web/src/components/tippen/Aquarium.tsx

@@ -90,7 +90,6 @@ export function Aquarium({ worlds, progress, nextLesson, onContinue, onOpenMap }
         )}
 
         <div style={{ display: "flex", justifyContent: "center", gap: 30, marginTop: 14 }}>
-          <Stat label="Perlen" value={`🦪 ${progress.pearls}`} />
           <Stat label="Tage am Stück" value={`🔥 ${progress.streak.days}`} />
           <Stat
             label="Schnellstes Tier"

web/src/components/tippen/ResultSheet.tsx

@@ -93,7 +93,6 @@ export function ResultSheet({
         <div style={{ display: "flex", justifyContent: "center", gap: 26, marginTop: 12 }}>
           <Stat label="Richtig" value={`${Math.round(result.accuracy * 100)}%`} />
           <Stat label="Zeichen/Min" value={String(Math.round(result.speed))} />
-          <Stat label="Perlen" value={`+${result.pearls}`} />
         </div>
 
         {/* How close the next animal is. A near miss is the strongest reason to press