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/domain/read_progress.rs

@@ -0,0 +1,50 @@
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use sqlx::FromRow;
+use uuid::Uuid;
+
+#[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
+pub struct ReadProgress {
+    pub user_id: Uuid,
+    pub manga_id: Uuid,
+    pub chapter_id: Option<Uuid>,
+    pub page: i32,
+    pub updated_at: DateTime<Utc>,
+}
+
+/// Enriched row for the history view — joins in the manga's title and
+/// cover plus the chapter number (when the chapter still exists) so a
+/// card can render without extra round-trips.
+#[derive(Debug, Clone, Serialize, FromRow)]
+pub struct ReadProgressSummary {
+    pub manga_id: Uuid,
+    pub manga_title: String,
+    pub manga_cover_image_path: Option<String>,
+    pub chapter_id: Option<Uuid>,
+    /// `None` when the chapter was deleted after this row was written
+    /// (FK ON DELETE SET NULL on `chapter_id`).
+    pub chapter_number: Option<i32>,
+    pub page: i32,
+    pub updated_at: DateTime<Utc>,
+}
+
+/// Returned by `GET /me/read-progress/:manga_id`. Same shape as
+/// `ReadProgressSummary` minus the manga title/cover (the caller
+/// already knows them — they're on the manga detail page). Crucially
+/// includes `chapter_number` so the "Continue reading" CTA can render
+/// without resolving the chapter id against a paged chapters list.
+#[derive(Debug, Clone, Serialize, FromRow)]
+pub struct ReadProgressForManga {
+    pub manga_id: Uuid,
+    pub chapter_id: Option<Uuid>,
+    pub chapter_number: Option<i32>,
+    pub page: i32,
+    pub updated_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct UpsertReadProgress {
+    pub manga_id: Uuid,
+    pub chapter_id: Option<Uuid>,
+    pub page: Option<i32>,
+}