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/src/repo/chapter.rs

@@ -52,22 +52,28 @@ pub async fn find_by_manga_and_number(
 /// transaction with the per-page inserts. Returns `AppError::Conflict`
 /// on the (manga_id, number) unique violation so handlers can surface a
 /// clean 409.
+///
+/// `uploaded_by` records who uploaded the chapter and feeds the
+/// per-user upload history. `None` means "historical / API token with
+/// no associated user" — kept nullable to support that case.
 pub async fn create<'e, E: PgExecutor<'e>>(
     executor: E,
     manga_id: Uuid,
     number: i32,
     title: Option<&str>,
+    uploaded_by: Option<Uuid>,
 ) -> AppResult<Chapter> {
     let result = sqlx::query_as::<_, Chapter>(
         r#"
-        INSERT INTO chapters (manga_id, number, title)
-        VALUES ($1, $2, $3)
+        INSERT INTO chapters (manga_id, number, title, uploaded_by)
+        VALUES ($1, $2, $3, $4)
         RETURNING id, manga_id, number, title, page_count, created_at
         "#,
     )
     .bind(manga_id)
     .bind(number)
     .bind(title)
+    .bind(uploaded_by)
     .fetch_one(executor)
     .await;