feat(stats): build anime-centric stats dashboard frontend

5-tab React dashboard with Catppuccin Mocha theme:
- Overview: hero stats, streak calendar, watch time chart, recent sessions
- Anime: grid with cover art, episode list with completion %, detail view
- Trends: 15 charts across Activity, Efficiency, Anime, and Patterns
- Vocabulary: POS-filtered word/kanji lists with detail panels
- Sessions: expandable session history with event timeline

Features:
- Cross-tab navigation (anime <-> vocabulary)
- Global word detail panel overlay
- Expandable episode detail with Anki card links (Expression field)
- Per-anime multi-line trend charts
- Watch time by day-of-week and hour-of-day
- Collapsible sections with accessibility (aria-expanded)
- Card size selector for anime grid
- Cover art caching via AniList
- HTTP API client with file:// protocol fallback for Electron overlay

stats/src/types/stats.ts

@@ -0,0 +1,285 @@
+export interface SessionSummary {
+  sessionId: number;
+  canonicalTitle: string | null;
+  videoId: number | null;
+  animeId: number | null;
+  animeTitle: string | null;
+  startedAtMs: number;
+  endedAtMs: number | null;
+  totalWatchedMs: number;
+  activeWatchedMs: number;
+  linesSeen: number;
+  wordsSeen: number;
+  tokensSeen: number;
+  cardsMined: number;
+  lookupCount: number;
+  lookupHits: number;
+}
+
+export interface DailyRollup {
+  rollupDayOrMonth: number;
+  videoId: number | null;
+  totalSessions: number;
+  totalActiveMin: number;
+  totalLinesSeen: number;
+  totalWordsSeen: number;
+  totalTokensSeen: number;
+  totalCards: number;
+  cardsPerHour: number | null;
+  wordsPerMin: number | null;
+  lookupHitRate: number | null;
+}
+
+export type MonthlyRollup = DailyRollup;
+
+export interface SessionTimelinePoint {
+  sampleMs: number;
+  totalWatchedMs: number;
+  activeWatchedMs: number;
+  linesSeen: number;
+  wordsSeen: number;
+  tokensSeen: number;
+  cardsMined: number;
+}
+
+export interface SessionEvent {
+  eventType: EventType;
+  tsMs: number;
+  payload: string | null;
+}
+
+export interface VocabularyEntry {
+  wordId: number;
+  headword: string;
+  word: string;
+  reading: string;
+  partOfSpeech: string | null;
+  pos1: string | null;
+  pos2: string | null;
+  pos3: string | null;
+  frequency: number;
+  firstSeen: number;
+  lastSeen: number;
+}
+
+export interface KanjiEntry {
+  kanjiId: number;
+  kanji: string;
+  frequency: number;
+  firstSeen: number;
+  lastSeen: number;
+}
+
+export interface VocabularyOccurrenceEntry {
+  animeId: number | null;
+  animeTitle: string | null;
+  videoId: number;
+  videoTitle: string;
+  sessionId: number;
+  lineIndex: number;
+  segmentStartMs: number | null;
+  segmentEndMs: number | null;
+  text: string;
+  occurrenceCount: number;
+}
+
+export interface OverviewData {
+  sessions: SessionSummary[];
+  rollups: DailyRollup[];
+  hints: {
+    totalSessions: number;
+    activeSessions: number;
+    episodesToday: number;
+    activeAnimeCount: number;
+  };
+}
+
+export interface MediaLibraryItem {
+  videoId: number;
+  canonicalTitle: string;
+  totalSessions: number;
+  totalActiveMs: number;
+  totalCards: number;
+  totalWordsSeen: number;
+  lastWatchedMs: number;
+  hasCoverArt: number;
+}
+
+export interface MediaDetailData {
+  detail: {
+    videoId: number;
+    canonicalTitle: string;
+    totalSessions: number;
+    totalActiveMs: number;
+    totalCards: number;
+    totalWordsSeen: number;
+    totalLinesSeen: number;
+    totalLookupCount: number;
+    totalLookupHits: number;
+  } | null;
+  sessions: SessionSummary[];
+  rollups: DailyRollup[];
+}
+
+export const EventType = {
+  SUBTITLE_LINE: 1,
+  MEDIA_BUFFER: 2,
+  LOOKUP: 3,
+  CARD_MINED: 4,
+  SEEK_FORWARD: 5,
+  SEEK_BACKWARD: 6,
+  PAUSE_START: 7,
+  PAUSE_END: 8,
+} as const;
+
+export type EventType = (typeof EventType)[keyof typeof EventType];
+
+export interface AnimeLibraryItem {
+  animeId: number;
+  canonicalTitle: string;
+  anilistId: number | null;
+  totalSessions: number;
+  totalActiveMs: number;
+  totalCards: number;
+  totalWordsSeen: number;
+  episodeCount: number;
+  episodesTotal: number | null;
+  lastWatchedMs: number;
+}
+
+export interface AnilistEntry {
+  anilistId: number;
+  titleRomaji: string | null;
+  titleEnglish: string | null;
+  season: number | null;
+}
+
+export interface AnimeDetailData {
+  detail: {
+    animeId: number;
+    canonicalTitle: string;
+    anilistId: number | null;
+    titleRomaji: string | null;
+    titleEnglish: string | null;
+    titleNative: string | null;
+    totalSessions: number;
+    totalActiveMs: number;
+    totalCards: number;
+    totalWordsSeen: number;
+    totalLinesSeen: number;
+    totalLookupCount: number;
+    totalLookupHits: number;
+    episodeCount: number;
+    lastWatchedMs: number;
+  };
+  episodes: AnimeEpisode[];
+  anilistEntries: AnilistEntry[];
+}
+
+export interface AnimeEpisode {
+  videoId: number;
+  episode: number | null;
+  season: number | null;
+  durationMs: number;
+  watched: number;
+  canonicalTitle: string;
+  totalSessions: number;
+  totalActiveMs: number;
+  totalCards: number;
+  lastWatchedMs: number;
+}
+
+export interface AnimeWord {
+  wordId: number;
+  headword: string;
+  word: string;
+  reading: string;
+  partOfSpeech: string | null;
+  frequency: number;
+}
+
+export interface StreakCalendarDay {
+  epochDay: number;
+  totalActiveMin: number;
+}
+
+export interface EpisodesPerDay {
+  epochDay: number;
+  episodeCount: number;
+}
+
+export interface NewAnimePerDay {
+  epochDay: number;
+  newAnimeCount: number;
+}
+
+export interface WatchTimePerAnime {
+  epochDay: number;
+  animeId: number;
+  animeTitle: string;
+  totalActiveMin: number;
+}
+
+export interface WordDetailData {
+  detail: {
+    wordId: number;
+    headword: string;
+    word: string;
+    reading: string;
+    partOfSpeech: string | null;
+    pos1: string | null;
+    pos2: string | null;
+    pos3: string | null;
+    frequency: number;
+    firstSeen: number;
+    lastSeen: number;
+  };
+  animeAppearances: Array<{
+    animeId: number;
+    animeTitle: string;
+    occurrenceCount: number;
+  }>;
+  similarWords: Array<{
+    wordId: number;
+    headword: string;
+    word: string;
+    reading: string;
+    frequency: number;
+  }>;
+}
+
+export interface EpisodeCardEvent {
+  eventId: number;
+  sessionId: number;
+  tsMs: number;
+  cardsDelta: number;
+  noteIds: number[];
+}
+
+export interface EpisodeDetailData {
+  sessions: SessionSummary[];
+  words: AnimeWord[];
+  cardEvents: EpisodeCardEvent[];
+}
+
+export interface KanjiDetailData {
+  detail: {
+    kanjiId: number;
+    kanji: string;
+    frequency: number;
+    firstSeen: number;
+    lastSeen: number;
+  };
+  animeAppearances: Array<{
+    animeId: number;
+    animeTitle: string;
+    occurrenceCount: number;
+  }>;
+  words: Array<{
+    wordId: number;
+    headword: string;
+    word: string;
+    reading: string;
+    frequency: number;
+  }>;
+}