Add AY25-26 periods for BRC/LRC; add UCB 2024-25 calendar periods

[matthew-li]

Changes

• Added AllocationPeriod entries:
  • For "Allowance Year 2025 - 2026" for BRC and LRC.
  • For UC Berkeley Academic Calendar semesters and summer sessions for BRC.

How to Test

• Ensure that the test suite passes.
• Review the code changes and add comments as needed.
  • In particular, double-check the dates against the calendar linked above.
• Manual Testing
  • For both BRC and LRC:
    • Run python manage.py create_allocation_periods --dry_run and ensure that the new periods are listed.
    • Re-run it without the dry run flag and ensure that the new periods are created.
      • Note: They should not appear in the new project request or renewal request flows.