Fe/be improve appointments

[dashaaaa21]

On teacherDetail changed validation - now description 500 characters
Improve validation

[Copilot]

Pull request overview

This PR improves request validation and authorization handling across the backend, and aligns the appointment “description” validation with the updated frontend rule (500 characters).

Changes:

• Add backend appointment description validation using a shared max-length constant (500 chars).
• Introduce reusable request validation helpers (validatePaginationParams, validateAuthorization) and apply them across multiple controllers.
• Update client-side description validation/UI from word-count to character-count (500 chars) and improve textarea labeling.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
server/src/validation/appointment/appointmentValidationMiddleware.ts	Adds optional description max-length validation using a shared constant.
server/src/utils/validation/requestValidation.util.ts	Introduces shared authorization + pagination validation helpers.
server/src/controllers/videoCall.controller.ts	Refactors auth checks to use validateAuthorization and changes role error responses.
server/src/controllers/upload.controller.ts	Refactors auth checks to use validateAuthorization for avatar upload/delete.
server/src/controllers/teacher.controller.ts	Refactors auth checks to use validateAuthorization.
server/src/controllers/student.controller.ts	Refactors auth checks to use validateAuthorization.
server/src/controllers/review.controller.ts	Refactors auth + pagination parsing using new helpers.
server/src/controllers/appointment.controller.ts	Refactors pagination parsing and auth checks using new helpers.
server/src/constants/validation.constants.ts	Adds server-side constant for max description length (500).
client/src/utils/appointmentDescription.validation.ts	Switches from word-count to character-count validation (500).
client/src/components/teacherSection/teacherSchedule/TeacherSchedule.tsx	Updates UI to show character count and improves textarea accessibility attributes.

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