Feature/pix 58 validate user join

[matteosusca]

No description provided.

[Copilot]

Pull request overview

This PR adds centralized Socket.IO lobby utilities and introduces server-side validation when a user joins a lobby (banned/capacity), while simplifying draw/batch-draw socket handlers.

Changes:

• Added reusable Socket.IO helpers for lobby user count, user listing, and broadcasting.
• Validated lobby join attempts against banned users and lobby capacity before completing the join flow.
• Refactored draw/batch-draw handling to use CanvasService.drawBatch and shared broadcast helpers.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
server/src/utils/socketUtils.ts	Introduces shared Socket.IO room helpers (counts, user listing, broadcast wrappers).
server/src/sockets/index.ts	Uses new helpers; adds join validation and refactors draw/draw_batch event logic.
server/src/services/lobby.service.ts	Adds reusable validation methods for join access and lobby capacity.
server/src/services/canvas.service.ts	Adds drawBatch to process and persist multiple pixel updates efficiently.
server/src/middlewares/permissionMiddleware.ts	Reuses lobby access validation from LobbyService (but leaves an unused import).
client/src/views/PlayView.vue	Moves onUnmounted import to the top-level import section.

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[Copilot]

Capacity validation uses currentCount - 1 after an optimistic socket.join(), which makes the intent (checking count before vs after the join) hard to follow and easy to get wrong later. Consider computing a clearly named countBeforeJoin (or validating using the post-join count and checking > maxCollaborators) to make the off-by-one behavior explicit.