feat: add backup/restore of app configurations

Add export and import functionality for app configurations:

- Export single app or all apps as versioned JSON backup bundle
- Import from backup file with name-conflict detection (skip duplicates)
- Fresh SSH keys and webhook secrets generated on import
- Preserves env vars, labels, volumes, and port mappings
- Web UI: export button on app detail, backup/restore page on dashboard
- REST API: GET /api/v1/apps/{id}/export, GET /api/v1/backup/export,
  POST /api/v1/backup/import
- Comprehensive test coverage for service and handler layers

internal/handlers/backup.go

@@ -0,0 +1,282 @@
+package handlers
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/internal/service/app"
+	"sneak.berlin/go/upaas/templates"
+)
+
+// importMaxBodyBytes is the maximum allowed request body size for backup import (10 MB).
+const importMaxBodyBytes = 10 << 20
+
+// HandleExportApp exports a single app's configuration as a JSON download.
+func (h *Handlers) HandleExportApp() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+
+		application, findErr := models.FindApp(request.Context(), h.db, appID)
+		if findErr != nil || application == nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		bundle, exportErr := h.appService.ExportApp(request.Context(), application)
+		if exportErr != nil {
+			h.log.Error("failed to export app", "error", exportErr, "app", application.Name)
+			http.Error(writer, "Internal Server Error", http.StatusInternalServerError)
+
+			return
+		}
+
+		filename := fmt.Sprintf("upaas-backup-%s-%s.json",
+			application.Name,
+			time.Now().UTC().Format("20060102-150405"),
+		)
+
+		writer.Header().Set("Content-Type", "application/json")
+		writer.Header().Set("Content-Disposition",
+			`attachment; filename="`+filename+`"`)
+
+		encoder := json.NewEncoder(writer)
+		encoder.SetIndent("", "  ")
+
+		err := encoder.Encode(bundle)
+		if err != nil {
+			h.log.Error("failed to encode backup", "error", err)
+		}
+	}
+}
+
+// HandleExportAllApps exports all app configurations as a JSON download.
+func (h *Handlers) HandleExportAllApps() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		bundle, exportErr := h.appService.ExportAllApps(request.Context())
+		if exportErr != nil {
+			h.log.Error("failed to export all apps", "error", exportErr)
+			http.Error(writer, "Internal Server Error", http.StatusInternalServerError)
+
+			return
+		}
+
+		filename := fmt.Sprintf("upaas-backup-all-%s.json",
+			time.Now().UTC().Format("20060102-150405"),
+		)
+
+		writer.Header().Set("Content-Type", "application/json")
+		writer.Header().Set("Content-Disposition",
+			`attachment; filename="`+filename+`"`)
+
+		encoder := json.NewEncoder(writer)
+		encoder.SetIndent("", "  ")
+
+		err := encoder.Encode(bundle)
+		if err != nil {
+			h.log.Error("failed to encode backup", "error", err)
+		}
+	}
+}
+
+// HandleImportPage renders the import/restore page.
+func (h *Handlers) HandleImportPage() http.HandlerFunc {
+	tmpl := templates.GetParsed()
+
+	return func(writer http.ResponseWriter, request *http.Request) {
+		data := h.addGlobals(map[string]any{
+			"Success": request.URL.Query().Get("success"),
+		}, request)
+
+		h.renderTemplate(writer, tmpl, "backup_import.html", data)
+	}
+}
+
+// HandleImportApps processes an uploaded backup JSON file and imports apps.
+func (h *Handlers) HandleImportApps() http.HandlerFunc {
+	tmpl := templates.GetParsed()
+
+	return func(writer http.ResponseWriter, request *http.Request) {
+		bundle, parseErr := h.parseBackupUpload(request)
+		if parseErr != "" {
+			data := h.addGlobals(map[string]any{"Error": parseErr}, request)
+			h.renderTemplate(writer, tmpl, "backup_import.html", data)
+
+			return
+		}
+
+		imported, skipped, importErr := h.appService.ImportApps(
+			request.Context(), bundle,
+		)
+		if importErr != nil {
+			h.log.Error("failed to import apps", "error", importErr)
+
+			data := h.addGlobals(map[string]any{
+				"Error": "Import failed: " + importErr.Error(),
+			}, request)
+			h.renderTemplate(writer, tmpl, "backup_import.html", data)
+
+			return
+		}
+
+		successMsg := fmt.Sprintf("Imported %d app(s)", len(imported))
+		if len(skipped) > 0 {
+			successMsg += fmt.Sprintf(", skipped %d (name conflict)", len(skipped))
+		}
+
+		http.Redirect(writer, request,
+			"/backup/import?success="+successMsg,
+			http.StatusSeeOther,
+		)
+	}
+}
+
+// parseBackupUpload extracts and validates a BackupBundle from a multipart upload.
+// Returns the bundle and an empty string on success, or nil and an error message.
+func (h *Handlers) parseBackupUpload(
+	request *http.Request,
+) (*app.BackupBundle, string) {
+	request.Body = http.MaxBytesReader(nil, request.Body, importMaxBodyBytes)
+
+	parseErr := request.ParseMultipartForm(importMaxBodyBytes)
+	if parseErr != nil {
+		return nil, "Failed to parse upload: " + parseErr.Error()
+	}
+
+	file, _, openErr := request.FormFile("backup_file")
+	if openErr != nil {
+		return nil, "Please select a backup file to import"
+	}
+
+	defer func() { _ = file.Close() }()
+
+	var bundle app.BackupBundle
+
+	decodeErr := json.NewDecoder(file).Decode(&bundle)
+	if decodeErr != nil {
+		return nil, "Invalid backup file: " + decodeErr.Error()
+	}
+
+	if bundle.Version != 1 {
+		return nil, fmt.Sprintf(
+			"Unsupported backup version: %d (expected 1)", bundle.Version,
+		)
+	}
+
+	if len(bundle.Apps) == 0 {
+		return nil, "Backup file contains no apps"
+	}
+
+	return &bundle, ""
+}
+
+// HandleAPIExportApp exports a single app's configuration as JSON via API.
+func (h *Handlers) HandleAPIExportApp() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+
+		application, err := h.appService.GetApp(request.Context(), appID)
+		if err != nil {
+			h.respondJSON(writer, request,
+				map[string]string{"error": "internal server error"},
+				http.StatusInternalServerError)
+
+			return
+		}
+
+		if application == nil {
+			h.respondJSON(writer, request,
+				map[string]string{"error": "app not found"},
+				http.StatusNotFound)
+
+			return
+		}
+
+		bundle, exportErr := h.appService.ExportApp(request.Context(), application)
+		if exportErr != nil {
+			h.log.Error("failed to export app", "error", exportErr)
+			h.respondJSON(writer, request,
+				map[string]string{"error": "failed to export app"},
+				http.StatusInternalServerError)
+
+			return
+		}
+
+		h.respondJSON(writer, request, bundle, http.StatusOK)
+	}
+}
+
+// HandleAPIExportAllApps exports all app configurations as JSON via API.
+func (h *Handlers) HandleAPIExportAllApps() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		bundle, exportErr := h.appService.ExportAllApps(request.Context())
+		if exportErr != nil {
+			h.log.Error("failed to export all apps", "error", exportErr)
+			h.respondJSON(writer, request,
+				map[string]string{"error": "failed to export apps"},
+				http.StatusInternalServerError)
+
+			return
+		}
+
+		h.respondJSON(writer, request, bundle, http.StatusOK)
+	}
+}
+
+// HandleAPIImportApps imports app configurations from a JSON request body via API.
+func (h *Handlers) HandleAPIImportApps() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		request.Body = http.MaxBytesReader(writer, request.Body, importMaxBodyBytes)
+
+		var bundle app.BackupBundle
+
+		decodeErr := json.NewDecoder(request.Body).Decode(&bundle)
+		if decodeErr != nil {
+			h.respondJSON(writer, request,
+				map[string]string{"error": "invalid request body"},
+				http.StatusBadRequest)
+
+			return
+		}
+
+		if bundle.Version != 1 {
+			h.respondJSON(writer, request,
+				map[string]string{"error": fmt.Sprintf(
+					"unsupported backup version: %d", bundle.Version,
+				)},
+				http.StatusBadRequest)
+
+			return
+		}
+
+		if len(bundle.Apps) == 0 {
+			h.respondJSON(writer, request,
+				map[string]string{"error": "backup contains no apps"},
+				http.StatusBadRequest)
+
+			return
+		}
+
+		imported, skipped, importErr := h.appService.ImportApps(
+			request.Context(), &bundle,
+		)
+		if importErr != nil {
+			h.log.Error("api: failed to import apps", "error", importErr)
+			h.respondJSON(writer, request,
+				map[string]string{"error": "import failed: " + importErr.Error()},
+				http.StatusInternalServerError)
+
+			return
+		}
+
+		h.respondJSON(writer, request, map[string]any{
+			"imported": imported,
+			"skipped":  skipped,
+		}, http.StatusOK)
+	}
+}