fix(planner): align protein gradient CSS vars with actual seed tag names

- Rename --gradient-protein-ei → --gradient-protein-eier (tag is 'Eier')
- Add --gradient-protein-kaese for tag 'Käse' (was missing entirely)

The only protein tags in seed data are Käse, Hülsenfrüchte, Eier.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/app.css

@@ -100,7 +100,8 @@
 	--gradient-protein-vegetarisch: linear-gradient(135deg, #86efac 0%, #4ade80 100%);
 	--gradient-protein-schwein: linear-gradient(135deg, #fca5a5 0%, #f87171 100%);
 	--gradient-protein-lamm: linear-gradient(135deg, #92400e 0%, #78350f 100%);
-	--gradient-protein-ei: linear-gradient(135deg, #fbbf24 0%, #f59e0b 100%);
+	--gradient-protein-eier: linear-gradient(135deg, #fbbf24 0%, #f59e0b 100%);
+	--gradient-protein-kaese: linear-gradient(135deg, #fcd34d 0%, #d97706 100%);
 	--gradient-protein-huelsenfruechte: linear-gradient(135deg, #a16207 0%, #854d0e 100%);
 
 	/* ── Cuisine gradient tokens ────────────────────────────────────── */

frontend/src/lib/design-system/tokens.test.ts

@@ -60,7 +60,8 @@ const requiredTokens = [
 	'--gradient-protein-vegetarisch',
 	'--gradient-protein-schwein',
 	'--gradient-protein-lamm',
-	'--gradient-protein-ei',
+	'--gradient-protein-eier',
+	'--gradient-protein-kaese',
 	'--gradient-protein-huelsenfruechte',
 	// Cuisine gradient tokens
 	'--gradient-cuisine-italienisch',