add language learner project

Dutch and Korean (explained in English) and English (explained in Dutch)
from A1 to C1, with a Hangul level for Korean. Lessons with notes, words
and sentences generate multiple-choice, typing, sentence building, cloze,
listening and matching exercises. Endless challenges: a seeded daily
challenge, sprint, survival, mixed practice, level tests, spaced-repetition
reviews and generated drills (numbers, clock times, de/het, plurals, Dutch
and Korean conjugation, particles, Hangul reading, irregular verbs).
Progress is stored in localStorage with export/import.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lib/language-learner/modes.ts

@@ -0,0 +1,41 @@
+export type ModeId = 'daily' | 'sprint' | 'survival' | 'endless' | 'review';
+
+export type ModeInfo = {
+	id: ModeId;
+	title: string;
+	description: string;
+	group: 'challenge' | 'review';
+};
+
+export const MODES: ModeInfo[] = [
+	{
+		id: 'daily',
+		title: 'Daily challenge',
+		description: '20 questions, the same all day. Your first score counts.',
+		group: 'challenge'
+	},
+	{
+		id: 'sprint',
+		title: 'Sprint',
+		description: 'As many right answers as you can in 60 seconds.',
+		group: 'challenge'
+	},
+	{
+		id: 'survival',
+		title: 'Survival',
+		description: 'Endless and slowly harder. Three mistakes and you are out.',
+		group: 'challenge'
+	},
+	{
+		id: 'endless',
+		title: 'Mixed practice',
+		description: 'No timer, no lives. Words, grammar and drills until you stop.',
+		group: 'challenge'
+	},
+	{
+		id: 'review',
+		title: 'Review',
+		description: 'Spaced repetition: due words first, then your weakest ones.',
+		group: 'review'
+	}
+];