`e2e.acceptSuggestedGroupKey` endpoint still uses legacy `addRoute` pattern

[NAME-ASHWANIYADAV]

The e2e.acceptSuggestedGroupKey POST endpoint (apps/meteor/app/api/server/v1/e2e.ts) still uses the deprecated API.v1.addRoute pattern with validateParams.

It should be migrated to the new chained .post() API pattern with AJV validation, consistent with the already-migrated e2e.setRoomKeyID endpoint in the same file.

Files involved

• apps/meteor/app/api/server/v1/e2e.ts
• packages/rest-typings/src/v1/e2e.ts