feat: add download button to Tables/Images views, add task history delete/clear-all

web/backend/services/db_schema.py

@@ -333,6 +333,28 @@ def query_task_stats() -> dict:
         conn.close()
 
 
+def delete_task(task_id: str) -> bool:
+    """Delete a single task by ID. Returns True if deleted."""
+    conn = sqlite3.connect(_db_path)
+    try:
+        cur = conn.execute("DELETE FROM task_history WHERE id = ?", (task_id,))
+        conn.commit()
+        return cur.rowcount > 0
+    finally:
+        conn.close()
+
+
+def clear_task_history() -> int:
+    """Delete all task history records. Returns number of deleted rows."""
+    conn = sqlite3.connect(_db_path)
+    try:
+        cur = conn.execute("DELETE FROM task_history")
+        conn.commit()
+        return cur.rowcount
+    finally:
+        conn.close()
+
+
 # ---------------------------------------------------------------------------
 # Query functions — File metadata
 # ---------------------------------------------------------------------------