feat: edit existing env vars, labels, and volume mounts

Add inline edit functionality for environment variables, labels, and
volume mounts on the app detail page. Each entity row now has an Edit
button that reveals an inline form using Alpine.js.

- POST /apps/{id}/env-vars/{varID}/edit
- POST /apps/{id}/labels/{labelID}/edit
- POST /apps/{id}/volumes/{volumeID}/edit
- Path validation for volume host and container paths
- Warning banner about container restart after env var changes
- Tests for ValidateVolumePath

fixes #67

internal/handlers/app.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"database/sql"
 	"encoding/json"
+	"errors"
+	"fmt"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -1116,6 +1118,207 @@ func (h *Handlers) HandlePortDelete() http.HandlerFunc {
 	}
 }
 
+// ErrVolumePathEmpty is returned when a volume path is empty.
+var ErrVolumePathEmpty = errors.New("path must not be empty")
+
+// ErrVolumePathNotAbsolute is returned when a volume path is not absolute.
+var ErrVolumePathNotAbsolute = errors.New("path must be absolute")
+
+// ErrVolumePathNotClean is returned when a volume path is not clean.
+var ErrVolumePathNotClean = errors.New("path must be clean")
+
+// ValidateVolumePath checks that a path is absolute and clean.
+func ValidateVolumePath(p string) error {
+	if p == "" {
+		return ErrVolumePathEmpty
+	}
+
+	if !filepath.IsAbs(p) {
+		return ErrVolumePathNotAbsolute
+	}
+
+	cleaned := filepath.Clean(p)
+	if cleaned != p {
+		return fmt.Errorf("%w (expected %q)", ErrVolumePathNotClean, cleaned)
+	}
+
+	return nil
+}
+
+// HandleEnvVarEdit handles editing an existing environment variable.
+func (h *Handlers) HandleEnvVarEdit() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+		envVarIDStr := chi.URLParam(request, "varID")
+
+		envVarID, parseErr := strconv.ParseInt(envVarIDStr, 10, 64)
+		if parseErr != nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		envVar, findErr := models.FindEnvVar(request.Context(), h.db, envVarID)
+		if findErr != nil || envVar == nil || envVar.AppID != appID {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		formErr := request.ParseForm()
+		if formErr != nil {
+			http.Error(writer, "Bad Request", http.StatusBadRequest)
+
+			return
+		}
+
+		key := request.FormValue("key")
+		value := request.FormValue("value")
+
+		if key == "" || value == "" {
+			http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+
+			return
+		}
+
+		envVar.Key = key
+		envVar.Value = value
+
+		saveErr := envVar.Save(request.Context())
+		if saveErr != nil {
+			h.log.Error("failed to update env var", "error", saveErr)
+		}
+
+		http.Redirect(
+			writer,
+			request,
+			"/apps/"+appID+"?success=env-updated",
+			http.StatusSeeOther,
+		)
+	}
+}
+
+// HandleLabelEdit handles editing an existing label.
+func (h *Handlers) HandleLabelEdit() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+		labelIDStr := chi.URLParam(request, "labelID")
+
+		labelID, parseErr := strconv.ParseInt(labelIDStr, 10, 64)
+		if parseErr != nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		label, findErr := models.FindLabel(request.Context(), h.db, labelID)
+		if findErr != nil || label == nil || label.AppID != appID {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		formErr := request.ParseForm()
+		if formErr != nil {
+			http.Error(writer, "Bad Request", http.StatusBadRequest)
+
+			return
+		}
+
+		key := request.FormValue("key")
+		value := request.FormValue("value")
+
+		if key == "" || value == "" {
+			http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+
+			return
+		}
+
+		label.Key = key
+		label.Value = value
+
+		saveErr := label.Save(request.Context())
+		if saveErr != nil {
+			h.log.Error("failed to update label", "error", saveErr)
+		}
+
+		http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+	}
+}
+
+// HandleVolumeEdit handles editing an existing volume mount.
+func (h *Handlers) HandleVolumeEdit() http.HandlerFunc {
+	return func(writer http.ResponseWriter, request *http.Request) {
+		appID := chi.URLParam(request, "id")
+		volumeIDStr := chi.URLParam(request, "volumeID")
+
+		volumeID, parseErr := strconv.ParseInt(volumeIDStr, 10, 64)
+		if parseErr != nil {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		volume, findErr := models.FindVolume(request.Context(), h.db, volumeID)
+		if findErr != nil || volume == nil || volume.AppID != appID {
+			http.NotFound(writer, request)
+
+			return
+		}
+
+		formErr := request.ParseForm()
+		if formErr != nil {
+			http.Error(writer, "Bad Request", http.StatusBadRequest)
+
+			return
+		}
+
+		hostPath := request.FormValue("host_path")
+		containerPath := request.FormValue("container_path")
+		readOnly := request.FormValue("readonly") == "1"
+
+		if hostPath == "" || containerPath == "" {
+			http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+
+			return
+		}
+
+		pathErr := validateVolumePaths(hostPath, containerPath)
+		if pathErr != nil {
+			h.log.Error("invalid volume path", "error", pathErr)
+			http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+
+			return
+		}
+
+		volume.HostPath = hostPath
+		volume.ContainerPath = containerPath
+		volume.ReadOnly = readOnly
+
+		saveErr := volume.Save(request.Context())
+		if saveErr != nil {
+			h.log.Error("failed to update volume", "error", saveErr)
+		}
+
+		http.Redirect(writer, request, "/apps/"+appID, http.StatusSeeOther)
+	}
+}
+
+// validateVolumePaths validates both host and container paths for a volume.
+func validateVolumePaths(hostPath, containerPath string) error {
+	hostErr := ValidateVolumePath(hostPath)
+	if hostErr != nil {
+		return fmt.Errorf("host path: %w", hostErr)
+	}
+
+	containerErr := ValidateVolumePath(containerPath)
+	if containerErr != nil {
+		return fmt.Errorf("container path: %w", containerErr)
+	}
+
+	return nil
+}
+
 // formatDeployKey formats an SSH public key with a descriptive comment.
 // Format: ssh-ed25519 AAAA... upaas_2025-01-15_myapp
 func formatDeployKey(pubKey string, createdAt time.Time, appName string) string {