feat: Enhance task access control and session management

- Implemented API and web task access assertions in the task status polling endpoint.
- Added functions to remember and check task access in user sessions.
- Updated task status tests to validate access control based on session data.
- Enhanced download route tests to ensure proper access checks.
- Improved SEO metadata handling with dynamic social preview images.
- Updated sitemap generation to include blog posts and new tools.
- Added a social preview SVG for better sharing on social media platforms.

backend/app/utils/auth.py

@@ -1,6 +1,9 @@
 """Session helpers for authenticated routes."""
 from flask import session
 
+TASK_ACCESS_SESSION_KEY = "task_access_ids"
+MAX_TRACKED_TASK_IDS = 200
+
 
 def get_current_user_id() -> int | None:
     """Return the authenticated user id from session storage."""
@@ -8,11 +11,31 @@ def get_current_user_id() -> int | None:
     return user_id if isinstance(user_id, int) else None
 
 
+def remember_task_access(task_id: str):
+    """Persist one web task id in the active browser session."""
+    tracked = session.get(TASK_ACCESS_SESSION_KEY, [])
+    if not isinstance(tracked, list):
+        tracked = []
+
+    normalized = [value for value in tracked if isinstance(value, str) and value != task_id]
+    normalized.append(task_id)
+    session[TASK_ACCESS_SESSION_KEY] = normalized[-MAX_TRACKED_TASK_IDS:]
+
+
+def has_session_task_access(task_id: str) -> bool:
+    """Return whether the active browser session owns one web task id."""
+    tracked = session.get(TASK_ACCESS_SESSION_KEY, [])
+    return isinstance(tracked, list) and task_id in tracked
+
+
 def login_user_session(user_id: int):
     """Persist the authenticated user in the Flask session."""
+    tracked_task_ids = session.get(TASK_ACCESS_SESSION_KEY, [])
     session.clear()
     session.permanent = True
     session["user_id"] = user_id
+    if isinstance(tracked_task_ids, list) and tracked_task_ids:
+        session[TASK_ACCESS_SESSION_KEY] = tracked_task_ids[-MAX_TRACKED_TASK_IDS:]
 
 
 def logout_user_session():