feat: Enhance validation and permissions handling across controllers

- Added `ValidatedJson` extractor for automatic JSON validation in `events_controller.rs`, `testimonials_controller.rs`, `mentors_controller.rs`, `gacha_items_controller.rs`, and `hackathon_controller.rs`.
- Replaced manual permission checks with `require_permissions!` and `require_auth!` macros in relevant controllers to streamline permission handling.
- Introduced `sanitization` utilities in `sanitization.rs` for improved input sanitization.
- Added `permission_macros.rs` to encapsulate permission checking logic and reduce boilerplate.
- Updated dependencies in `Cargo.toml` to include `serde_json` and `validator`.
- Implemented error handling improvements in `notification_service.rs` for better response management.

Cargo.lock

@@ -2293,11 +2293,13 @@ dependencies = [
  "once_cell",
  "reqwest",
  "serde",
+ "serde_json",
  "sha2",
  "surrealdb",
  "tokio",
  "urlencoding",
  "uuid",
+ "validator",
 ]
 
 [[package]]
@@ -2342,6 +2344,7 @@ dependencies = [
  "imphnen-entities",
  "imphnen-libs",
  "rand 0.9.2",
+ "regex",
  "reqwest",
  "serde",
  "serde_json",