feat(stats): reading statistics — session capture wired + /stats page + widget + per-book card

The design parked in the handoff (multi-tier stats off reading_history;
bookorbit-style in data, not looks) is in. The real prerequisite work
was data: reading_history existed but NOTHING wrote to it — the whole
stats feature was sitting on an empty table.

- CAPTURE (no client changes, no repo-boundary crossings): every
  successful progress write through SaveProgress (KOReader + app + web
  + Kobo + offline queue — the one chokepoint) now records one
  reading_history session row: span = the interval since the PREVIOUS
  write instant, pages = positive page delta when both sides know the
  page index, marker rows for first contact. Spans over 2h are kept as
  zero-second markers (overnight suspend→resume, offline flushes must
  not inflate totals) — the honest 'sync cadence, not a stopwatch'
  caveat stays. device_id only when a REAL device row matches (the
  web/app progress path historically stuffs the USER id into DeviceID
  — probe instead of trusting it; FK violation would silently drop
  every capture). Source preserved in device_metadata.

- API: /api/stats/summary?range=7|30|90|year (totals, zero-filled
  daily arrays, streaks, most-active day/weekday, top books, library
  breakdown — one call), /api/stats/this-week (widget: rolling 7d vs
  previous + streak), /api/stats/books/:id (lifetime + recent
  sessions). All bucketed in the user's timezone; finished ≡ any push
  ≥0.995; visible-library lens enforced at source. Legacy
  /api/analytics/* kept untouched. Range windows anchor end-of-day to
  the START of today (blasting the clock time into tomorrow resolved
  'today' a calendar day late — found by the streak test).

- /stats page (sidebar Stats between Progress and Devices, previously
  /analytics was an orphan): range selector, five stat cards, two
  Chart.js v4 charts (daily minutes bar, pages/day line — chunked via
  dynamic import so main.js stays untouched), per-library breakdown,
  most-read list, empty-state explainer. /analytics now 301s to /stats.
  The orphaned analytics.templ + analytics.ts removed (their containers
  and the page JSON never matched; the page was astub).

- Dashboard 'This Week' widget (server-rendered, suppressed on service
  failure) and the book detail 'Your Reading Stats' card (lifetime
  totals of the viewer's own sessions) complete the tiers: per-user
  default, per-library breakdown inline, per-book on the page,
  per-system/admin aggregate parked as before.

Tests: statistics_test.go (capture semantics at the chokepoint,
tz/day buckets, zero-fill, streak math, finished detection, range
validation, auth gate, widget, per-book lifetime). Full suite PASS.

internal/database/querier.go

@@ -153,6 +153,10 @@ type Querier interface {
 	DeleteUnlinkedBook(ctx context.Context, id pgtype.UUID) error
 	DeleteUser(ctx context.Context, id pgtype.UUID) error
 	DeleteUserSystemCollection(ctx context.Context, arg DeleteUserSystemCollectionParams) error
+	// Device existence probe for capture: the web/app progress paths
+	// historically stuff the user id into DeviceID (it only fed a broadcast
+	// label before stats); a capture row must only reference a REAL device.
+	DeviceExistsForUser(ctx context.Context, arg DeviceExistsForUserParams) (bool, error)
 	// Find content-duplicate groups (same library + SHA-256, more than one row)
 	FindHashConflictGroups(ctx context.Context) ([]FindHashConflictGroupsRow, error)
 	GenerateKoboEntitlementId(ctx context.Context) (interface{}, error)
@@ -165,6 +169,8 @@ type Querier interface {
 	GetAllSystemSettings(ctx context.Context) ([]GetAllSystemSettingsRow, error)
 	GetAllSystemSettingsFull(ctx context.Context) ([]SystemSettings, error)
 	GetAnnotationsForBook(ctx context.Context, arg GetAnnotationsForBookParams) ([]GetAnnotationsForBookRow, error)
+	// Lifetime session rows for ONE book (the book-detail stats card).
+	GetBookReadingSessions(ctx context.Context, arg GetBookReadingSessionsParams) ([]GetBookReadingSessionsRow, error)
 	GetBooksByTag(ctx context.Context, arg GetBooksByTagParams) ([]MediaItems, error)
 	// Get collection
 	GetCollection(ctx context.Context, id pgtype.UUID) (Collections, error)
@@ -338,6 +344,8 @@ type Querier interface {
 	GetSystemSettingFull(ctx context.Context, settingKey string) (SystemSettings, error)
 	GetSystemTimezone(ctx context.Context) (string, error)
 	GetTombstonedAnnotationsForBook(ctx context.Context, arg GetTombstonedAnnotationsForBookParams) ([]GetTombstonedAnnotationsForBookRow, error)
+	// Most-read books for a range (minutes), for the top list.
+	GetTopBooksByMinutes(ctx context.Context, arg GetTopBooksByMinutesParams) ([]GetTopBooksByMinutesRow, error)
 	// Get universal progress for a book
 	GetUniversalProgress(ctx context.Context, arg GetUniversalProgressParams) (GetUniversalProgressRow, error)
 	// Get unlinked book by ContentId
@@ -354,12 +362,27 @@ type Querier interface {
 	// Get user device usage statistics
 	GetUserDeviceUsage(ctx context.Context, userID pgtype.UUID) ([]GetUserDeviceUsageRow, error)
 	GetUserForLogin(ctx context.Context, email string) (GetUserForLoginRow, error)
+	// Per-library aggregation for the same range.
+	GetUserLibraryBreakdown(ctx context.Context, arg GetUserLibraryBreakdownParams) ([]GetUserLibraryBreakdownRow, error)
 	GetUserMediaItemsForSync(ctx context.Context, userID pgtype.UUID) ([]GetUserMediaItemsForSyncRow, error)
 	GetUserPasswordHash(ctx context.Context, id pgtype.UUID) (string, error)
 	GetUserProgressForBooks(ctx context.Context, arg GetUserProgressForBooksParams) ([]GetUserProgressForBooksRow, error)
+	// Distinct ACTIVE days (any captured session) bucketed in the user's
+	// timezone — the streak calendar. Scoped to a long look-back so the
+	// "longest streak" and a current streak longer than the selected range
+	// are both real.
+	GetUserReadingActiveDays(ctx context.Context, arg GetUserReadingActiveDaysParams) ([]string, error)
 	// Analytics queries
 	// Get user reading history for analytics
 	GetUserReadingHistory(ctx context.Context, arg GetUserReadingHistoryParams) ([]GetUserReadingHistoryRow, error)
+	// STATISTICS (reading sessions) — time spent, pages, streaks, breakdowns.
+	// Every stats query scopes to the requesting user's VISIBLE libraries
+	// (family lens at the source) and single scan of reading_history.
+	// Full session rows for a range (summary math runs in Go: tz buckets,
+	// streaks, finished-book detection). The bucket/range key is the session
+	// END instant (the push time; NULL falls back to created_at) — the same
+	// value the capture stamps every write with.
+	GetUserReadingSessionsRange(ctx context.Context, arg GetUserReadingSessionsRangeParams) ([]GetUserReadingSessionsRangeRow, error)
 	GetUserVisibleLibraries(ctx context.Context, userID pgtype.UUID) ([]GetUserVisibleLibrariesRow, error)
 	GetVisibleLibraryMediaCounts(ctx context.Context, userID pgtype.UUID) ([]GetVisibleLibraryMediaCountsRow, error)
 	// Smart ("dynamic") collections: rules are evaluated LIVE at render, so