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/manga.rs

@@ -181,17 +181,23 @@ pub async fn get_detail(pool: &PgPool, id: Uuid) -> AppResult<MangaDetail> {
 /// by the caller via `repo::author::set_for_manga` etc. in the same
 /// transaction. `status` is taken as a validated string — the handler
 /// is responsible for defaulting/validating it.
+///
+/// `uploaded_by` records who created the manga and feeds the per-user
+/// upload history. `None` means "historical / no associated user" —
+/// historic rows from before the uploader columns were added carry
+/// NULL.
 pub async fn create<'e, E: PgExecutor<'e>>(
     executor: E,
     title: &str,
     status: &str,
     description: Option<&str>,
     alt_titles: &[String],
+    uploaded_by: Option<Uuid>,
 ) -> AppResult<Manga> {
     let row = sqlx::query_as::<_, Manga>(&format!(
         r#"
-        INSERT INTO mangas (title, status, description, alt_titles)
-        VALUES ($1, $2, $3, $4)
+        INSERT INTO mangas (title, status, description, alt_titles, uploaded_by)
+        VALUES ($1, $2, $3, $4, $5)
         RETURNING {SELECT_COLS}
         "#
     ))
@@ -199,6 +205,7 @@ pub async fn create<'e, E: PgExecutor<'e>>(
     .bind(status)
     .bind(description)
     .bind(alt_titles)
+    .bind(uploaded_by)
     .fetch_one(executor)
     .await?;
     Ok(row)