feat(notification): implement MarkAllNotificationsAsRead API

[hvn2k1]

Follows #2751

What this PR does

Implements the MarkAllNotificationsAsRead RPC, the last remaining stub of the notification center backend: any authenticated console user can mark every published notification as read in one call.

Background / Why this PR is needed

The inbox's "mark all as read" action needs a bulk endpoint; looping mark_as_read from the client would be racy and slow. With this, all RFC 0047 backend APIs are implemented.

Points

• The whole operation is a single idempotent INSERT ... SELECT upserting read markers for every status = PUBLISHED AND deleted = false notification (INSERT IGNORE on MySQL, ON CONFLICT DO NOTHING on Postgres) — no per-row loop, and existing markers keep their original read_at.
• The account-created bound is intentionally NOT applied here: marking literally all published notifications keeps the read flag consistent across every tab, while the unread count/tab remain bounded as before.
• With no stubs left, the unused statusNotImplemented sentinel and the proto's "intentionally left empty" NOTE are removed; no generated files change (the comment never reached them).

[Copilot]

Pull request overview

Implements the final missing notification-center backend RPC, MarkAllNotificationsAsRead, enabling an authenticated console user to mark every published, non-deleted notification as read in a single bulk upsert.

Changes:

• Add bulk “mark all as read” SQL (INSERT … SELECT with conflict-ignore semantics) for both Postgres and MySQL, and expose it via NotificationStorage.
• Implement NotificationService.MarkAllNotificationsAsRead with authentication + transactional execution.
• Remove the old “not implemented” sentinel and the proto NOTE that is no longer accurate.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
proto/notification/service.proto	Removes outdated NOTE about empty request/response bodies.
pkg/notification/storage/postgres/sql/insert_all_notification_reads.sql	Adds Postgres bulk upsert to create missing read markers for all published notifications.
pkg/notification/storage/postgres/notification.go	Embeds and exposes MarkAllNotificationsAsRead in Postgres storage implementation.
pkg/notification/storage/postgres/notification_test.go	Adds unit test coverage for the new Postgres storage method (contains a gomock expectation issue).
pkg/notification/storage/notification.go	Extends NotificationStorage interface with MarkAllNotificationsAsRead.
pkg/notification/storage/mysql/sql/insert_all_notification_reads.sql	Adds MySQL bulk insert-ignore for read markers for all published notifications.
pkg/notification/storage/mysql/notification.go	Embeds and exposes MarkAllNotificationsAsRead in MySQL storage implementation.
pkg/notification/storage/mysql/notification_test.go	Adds unit test coverage for the new MySQL storage method (contains a gomock expectation issue).
pkg/notification/storage/mock/notification.go	Updates the gomock storage mock with the new interface method.
pkg/notification/api/error.go	Removes now-unused statusNotImplemented and its imports.
pkg/notification/api/api.go	Implements the MarkAllNotificationsAsRead RPC with auth + transaction + storage call.
pkg/notification/api/api_test.go	Adds service-level unit tests for the new RPC behavior.

Files not reviewed (1)

• pkg/notification/storage/mock/notification.go: Generated file

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[Ubisoft-potato]

Nice work for notifation! 👍
Thanks!