feat: read & upload history (0.19.0)

Per-user reading progress and uploader attribution.

Schema (migration 0011): `read_progress` table (one row per (user,
manga); chapter_id nullable on chapter delete) and nullable
`uploaded_by` columns on mangas + chapters with partial indexes
scoped to non-null rows.

Endpoints (all `/me/*`, auth-scoped):
- PUT `/v1/me/read-progress` upserts. FK violations + cross-manga
  chapter ids both surface as 4xx (404 / 422) so the API can't be
  used to write logically invalid rows.
- GET `/v1/me/read-progress` paged newest-first list.
- GET `/v1/me/read-progress/:manga_id` enriched with chapter_number
  for the manga page's Continue CTA.
- DELETE `/v1/me/read-progress/:manga_id` idempotent.
- GET `/v1/me/uploads` interleaved manga + chapter uploads as a
  tagged union; limit-only pagination.

Existing manga + chapter upload handlers stamp `uploaded_by`.

Frontend:
- Reader emits progress on mount + page change (debounce) and via
  IntersectionObserver in continuous mode. High-water mark is seeded
  from the persisted server value so re-opening a chapter doesn't
  regress to page 1. Tab close survives via `sendBeacon` (fallback
  `keepalive` fetch); SPA navigation flushes via regular fetch.
- Manga detail page shows "Continue reading Chapter N — page M"
  above the chapters list, working even for mangas with >50
  chapters.
- New `/profile/history` tab with reading history (clear-per-row,
  inline error on failure) and uploads (mangas + chapters mixed
  chronologically with type-aware rendering).

171 backend tests (incl. 16 history tests covering ownership, FK
race, cross-link guard, chapter SET NULL behaviour) and 97 frontend
tests + svelte-check clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/tests/api_bookmarks.rs

@@ -344,7 +344,7 @@ async fn list_me_enriches_chapter_bookmarks_with_chapter_number(pool: PgPool) {
     let (_, cookie) = common::register_user(&h.app).await;
     let manga_id = common::seed_manga_via_api(&h.app, &cookie, "Berserk").await;
     // Seed a chapter directly so we know its number without uploading pages.
-    mangalord::repo::chapter::create(&pool, manga_id, 7, Some("The Brand"))
+    mangalord::repo::chapter::create(&pool, manga_id, 7, Some("The Brand"), None)
         .await
         .unwrap();
     // Look up its id so we can bookmark it.