feat : add project archiving feature

Allow projects to be archived/unarchived from the ProjectDrawer, with a
toggle filter on the projects page to show/hide archived projects.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/services/dto/project.ts

@@ -10,6 +10,7 @@ export type Project = {
     client: Client | null
     giteaOwner: string | null
     giteaRepo: string | null
+    archived: boolean
 }
 
 export type ProjectWrite = {
@@ -20,4 +21,5 @@ export type ProjectWrite = {
     client: string | null  // IRI : "/api/clients/1" ou null
     giteaOwner?: string | null
     giteaRepo?: string | null
+    archived?: boolean
 }