refactor(tenant): drop legacy plugin_installations, migrate monitoring to desktop_clients

Hard cutover from the browser-extension plugin flow to desktop clients:
remove plugin_installations/plugin_sessions tables and related service,
handler, router, and generated model code; migrate monitoring quotas
and collector types to desktop_clients (UUID primary_client_id);
recreate platform_access_snapshots keyed by client_id; update dev-seed
and callback types accordingly; mark legacy design docs as historical.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/transport/router.go

@@ -16,10 +16,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	publicAssets := NewAssetHandler(app)
 	app.Engine.GET("/api/public/assets/:token", publicAssets.Serve)
 
-	pluginHandler := NewMediaHandler(app)
-	callbacks := app.Engine.Group("/api/callback/plugin")
-	callbacks.POST("/bind", pluginHandler.PluginBindCallback)
-	callbacks.POST("/publish", pluginHandler.PluginPublishCallback)
+	mediaHandler := NewMediaHandler(app)
 
 	protected := app.Engine.Group("/api")
 	protected.Use(auth.Middleware(app.JWT, app.Sessions))
@@ -65,7 +62,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	tenantProtected.POST("/publish-jobs", publishJobHandler.Create)
 
 	media := tenantProtected.Group("/media")
-	media.GET("/platforms", pluginHandler.ListPlatforms)
+	media.GET("/platforms", mediaHandler.ListPlatforms)
 
 	workspace := tenantProtected.Group("/workspace")
 	wsHandler := NewWorkspaceHandler(app)
@@ -149,8 +146,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	articles.PUT("/:id", artHandler.Update)
 	articles.GET("/:id/stream", artHandler.Stream)
 	articles.GET("/:id/versions", artHandler.Versions)
-	articles.GET("/:id/publish-records", pluginHandler.ListPublishRecords)
-	articles.POST("/:id/publish-batches", pluginHandler.CreatePublishBatch)
+	articles.GET("/:id/publish-records", mediaHandler.ListPublishRecords)
 	articles.DELETE("/:id", artHandler.Delete)
 
 	brands := tenantProtected.Group("/brands")