Update seat allocation logic in random_algo for course and programme

[vikrantwiz02]

This pull request updates the seat allocation logic in the random_algo function to more accurately track already allotted seats and handle cases where no next priority registration is found. The most important changes are:

Seat allocation accuracy:

• The seats_alloted dictionary is now initialized with the actual count of FinalRegistration entries matching the current course, semester, batch, and programme type, instead of always starting from zero. This ensures that the algorithm accounts for seats already allotted before running.

Robustness in priority assignment:

• When searching for the next priority registration, the code now uses .filter().first() instead of .get(), preventing exceptions if no matching registration is found. If no next registration exists, the remaining seat count (rem) is decremented accordingly, ensuring the algorithm doesn't get stuck or raise errors.