This fixes a bug which caused fetching saved filter and favorite projects to crash, because the respective project ID is not a valid project id without special handling.
This fixes a bug where a saved filter would contain many "dead" entries for tasks which are not part of that filter. These entries were "dead" because the filter would not match for them and thus they were not shown.
The problem was caused by a routine during the creation of the filter where all projects from all matching tasks would be used as input for fetching the tasks to add to task_positions.
https://community.vikunja.io/t/not-able-to-move-task-between-buckets-within-a-kanban-view-for-saved-filter/2882/3
Before this fix, creating a project with Typesense enabled would fail with an error because the tasks it fetches as part of that process do not have the task position property in their index. We now fall back to using the db for searching in that case.
In the long run, we should use typesense joins for the task position to make this more efficient.
BREAKING CHANGE: the position of tasks now can't be updated anymore via the task update endpoint. Instead, there is a new endpoint which takes the project view into account as well.
