Add search by title for the 'my tasks' endpoint

[solenuk]

As an Org or Admin I want to search my own tasks by title from the "my tasks" list so that I can quickly find a specific task without scrolling through the whole list.

Assumptions & Constraints

• Search matches against title only, case insensitive, partial match, not an exact match.
• The search parameter is optional, when it's missing or blank, the endpoint behaves exactly as it does today.
• Search only applies within the caller's own tasks, it doesn't change which tasks a user can see, only narrows within what they already own.
• Pagination stays as is, search doesn't change the response shape, just which rows come back.

Preconditions

1. GET /api/v1/tasks/my already exists.

Business rules

1. A blank or missing search value returns the same result as today, all of the caller's owned tasks.
2. A search value matches any task whose title contains it, ignoring case.
3. Search never returns a task the caller doesn't own.

Acceptance Criteria

• GET /api/v1/tasks/my accepts an optional search query parameter.
• Passing a search value returns only owned tasks whose title contains that value, case insensitive.
• Leaving search empty or out entirely returns the full list, unchanged from current behavior.
• Pagination continues to work correctly together with search.

Out of scope

• Searching by description or any other field.
• Applying this same search to getAllTasks or any other endpoint.
• Any change to the frontend list page beyond what's needed to pass the parameter through.

Epic link
Epic #6 - EPIC: Tasks

Tasks

• Add the search query parameter to getMyTasks in TaskController.
• Add a repository method that filters by owner and title, case insensitive.
• Wire the parameter through TaskService.getAllMyTasks.
• Confirm search with a value, an empty value, and no value all behave correctly.