Add new tasks

[aVitness]

No description provided.

[vtm9]

The new tasks are useful, but this PR is not ready to merge against current main.

1. All 24 new task files omit required base_score, so the current make check-limits cannot accept them. Add scores within the level limits and below time_to_solve_sec.
2. game_of_life_step and valid_sudoku use 600 seconds for medium tasks; the maximum is 450. peak_performance_sum, valid_sudoku, and minimum_bracket_reversals also need paths matching tasks/<level>/<tags[0]>/<name>.toml.
3. flood_fill fails on an allowed input: solution([[0] * 50 for _ in range(50)], 0, 0, 1) raises RecursionError with the default Python recursion limit. Use an iterative traversal and add this boundary case.

The 671 submitted asserts pass, but they do not cover this valid flood-fill boundary. Please address these blockers and run the current make build.