Accounts Phase 3: save articles, account history, device import

- API (auth-required): GET/POST/DELETE /api/saved (+/api/saved/ids), GET/POST
  /api/history, POST /api/import — all FK-safe (skip ids that no longer exist).
  queries.saved/saved_ids/history reuse the feed article shape.
- Frontend: reactive savedIds store (SvelteSet) + optimistic toggleSave; a Save
  control on cards for signed-in users; a "Saved" view (You sheet) with its own
  empty state; newly-seen items mirror to account history (cross-device); and a
  one-time import folds this device's anonymous history into the account on first
  sign-in. Anonymous browsing unchanged. 115 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/queries.py

@@ -153,6 +153,60 @@ def brief(conn: sqlite3.Connection, brief_date: str | None = None, limit: int =
     }
 
 
+def saved(conn: sqlite3.Connection, user_id: int, limit: int = 200) -> list[dict]:
+    """Articles a user has saved, newest first (same shape as the feed)."""
+    rows = conn.execute(
+        f"""
+        SELECT {_ARTICLE_COLUMNS}
+        FROM saved_articles sv
+        JOIN articles a ON a.id = sv.article_id
+        JOIN sources src ON src.id = a.source_id
+        LEFT JOIN article_scores s ON s.article_id = a.id
+        WHERE sv.user_id = ?
+        ORDER BY sv.saved_at DESC
+        LIMIT ?
+        """,
+        (user_id, limit),
+    ).fetchall()
+    return [dict(row) for row in rows]
+
+
+def saved_ids(conn: sqlite3.Connection, user_id: int) -> list[int]:
+    return [r[0] for r in conn.execute(
+        "SELECT article_id FROM saved_articles WHERE user_id = ?", (user_id,)
+    )]
+
+
+def history(conn: sqlite3.Connection, user_id: int, limit: int = 200) -> list[dict]:
+    """Articles in a user's account history, most-recent first."""
+    rows = conn.execute(
+        f"""
+        SELECT {_ARTICLE_COLUMNS}, MAX(h.at) AS seen_at
+        FROM user_history h
+        JOIN articles a ON a.id = h.article_id
+        JOIN sources src ON src.id = a.source_id
+        LEFT JOIN article_scores s ON s.article_id = a.id
+        WHERE h.user_id = ?
+        GROUP BY a.id
+        ORDER BY seen_at DESC
+        LIMIT ?
+        """,
+        (user_id, limit),
+    ).fetchall()
+    return [dict(row) for row in rows]
+
+
+def existing_article_ids(conn: sqlite3.Connection, ids: list[int]) -> list[int]:
+    """Filter to ids that still exist (FK-safe inserts for save/history/import)."""
+    clean = list({int(i) for i in ids})[:1000]
+    if not clean:
+        return []
+    placeholders = ",".join("?" * len(clean))
+    return [r[0] for r in conn.execute(
+        f"SELECT id FROM articles WHERE id IN ({placeholders})", clean
+    )]
+
+
 def tag_counts(conn: sqlite3.Connection, accepted_only: bool = True) -> dict:
     """How many shown (accepted, non-duplicate) articles carry each grouping tag."""
     where = "WHERE a.duplicate_of IS NULL" + (" AND s.accepted = 1" if accepted_only else "")