Enhance course request views and notification handling

[vikrantwiz02]

This pull request introduces several improvements and bug fixes across academic procedures, notifications, and student management. The most significant changes include stricter and more accurate eligibility checks for PhD/PG course registration, improved notification handling (including a new bulk-clear endpoint), and more precise discipline assignment logic for student batches. Below are the most important changes grouped by theme:

Academic Procedures: PhD/PG Registration and Course Handling

• Improved PhD registration window logic to use academic term and year, ensuring correct eligibility checks for multiple intakes in a calendar year. PG registration continues to use semester and year.
• Enforced backlog (BL) course eligibility for PhD students, including grade checks at both the course listing and course submission stages, mirroring UG rules for backlog registration. [1] [2] [3]
• Enhanced PhD course registration approval to set the registration type (Regular, Backlog, Improvement) based on prior grades, and to record course replacements when a backlog/improvement registration is approved.
• Added discipline and specialization info to PhD admin request listings for better context. [1] [2]

Notifications: API and Bulk Operations

• Added a new endpoint and view to bulk-clear notifications or announcements for the authenticated user, respecting visibility rules and updating unread counts accordingly. [1] [2]
• Improved NotificationSerializer to robustly parse and return notification data as JSON, handling both string and dict payloads.

Student Management: Discipline Assignment

• Refined discipline assignment logic to match the most specific specialization name when assigning disciplines, preventing incorrect mappings due to substring overlaps (e.g., distinguishing 'mechatronics' from 'mechanical engineering'). Also, separated 'Design' specialization from other mechanical engineering specializations. [1] [2]