Add configuration revisions system and project variant deletion

Features:
- Configuration versioning: immutable snapshots in local_configuration_versions
- Revisions UI: /configs/:uuid/revisions page to view version history
- Clone from version: ability to clone configuration from specific revision
- Project variant deletion: DELETE /api/projects/:uuid endpoint
- Updated CLAUDE.md with new architecture details and endpoints

Architecture updates:
- local_configuration_versions table for immutable snapshots
- Version tracking on each configuration save
- Rollback capability to previous versions
- Variant deletion with main variant protection

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

cmd/qfs/main.go

@@ -930,6 +930,7 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 	router.GET("/configurator", webHandler.Configurator)
 	router.GET("/projects", webHandler.Projects)
 	router.GET("/projects/:uuid", webHandler.ProjectDetail)
+	router.GET("/configs/:uuid/revisions", webHandler.ConfigRevisions)
 	router.GET("/pricelists", webHandler.Pricelists)
 	router.GET("/pricelists/:id", webHandler.PricelistDetail)
 
@@ -1129,15 +1130,20 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 			configs.POST("/:uuid/clone", func(c *gin.Context) {
 				uuid := c.Param("uuid")
 				var req struct {
-					Name string `json:"name"`
+					Name        string `json:"name"`
+					FromVersion int    `json:"from_version"`
 				}
 				if err := c.ShouldBindJSON(&req); err != nil {
 					c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 					return
 				}
 
-				config, err := configService.CloneNoAuth(uuid, req.Name, dbUsername)
+				config, err := configService.CloneNoAuthToProjectFromVersion(uuid, req.Name, dbUsername, nil, req.FromVersion)
 				if err != nil {
+					if errors.Is(err, services.ErrConfigVersionNotFound) {
+						c.JSON(http.StatusNotFound, gin.H{"error": "version not found"})
+						return
+					}
 					c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 					return
 				}
@@ -1579,6 +1585,23 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 				c.JSON(http.StatusOK, gin.H{"message": "project reactivated"})
 			})
 
+			projects.DELETE("/:uuid", func(c *gin.Context) {
+				if err := projectService.DeleteVariant(c.Param("uuid"), dbUsername); err != nil {
+					switch {
+					case errors.Is(err, services.ErrCannotDeleteMainVariant):
+						c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+					case errors.Is(err, services.ErrProjectNotFound):
+						c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
+					case errors.Is(err, services.ErrProjectForbidden):
+						c.JSON(http.StatusForbidden, gin.H{"error": err.Error()})
+					default:
+						c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+					}
+					return
+				}
+				c.JSON(http.StatusOK, gin.H{"message": "variant deleted"})
+			})
+
 			projects.GET("/:uuid/configs", func(c *gin.Context) {
 				triggerPull("configs", &configsPullState, syncConfigurationsFromServer)