fix(web): disable delete confirms while pending + Signing in… feedback (#70)

The delete dialogs (DeleteObjectDialog and the shared
DeleteConfirmDialog) left their confirm button enabled during the
in-flight request, so a double-click fired a second DELETE that 404'd
and surfaced a spurious error. Disable cancel + confirm while pending
and swap the confirm label to a new actions.deleting ("Deleting…" /
"Tar bort…").

The login button disabled itself during login.isPending but kept the
"Sign in" label; it now shows auth.signingIn ("Signing in…" /
"Loggar in…") so slow networks get visible feedback.

Each fix is covered by a gated-MSW (or gated-promise) test asserting
the pending label + disabled state before releasing the request.

Closes #70

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/i18n/en.json

@@ -1,12 +1,12 @@
 {
   "common": { "yes": "Yes", "no": "No", "close": "Close", "loading": "Loading", "filter": "Filter…", "noMatches": "No matches", "language": "Language", "skipToContent": "Skip to content", "clear": "Clear", "open": "Open" },
   "nav": { "objects": "Objects", "vocabularies": "Vocabularies", "authorities": "Authorities", "fields": "Fields", "search": "Search", "collapseSidebar": "Collapse sidebar", "expandSidebar": "Expand sidebar", "breadcrumb": "Breadcrumb" },
-  "auth": { "email": "Email", "password": "Password", "signIn": "Sign in", "signOut": "Sign out", "invalid": "Invalid email or password", "networkError": "Could not reach the server", "sessionExpired": "Your session expired — please sign in again.", "signingOut": "Signing out…" },
+  "auth": { "email": "Email", "password": "Password", "signIn": "Sign in", "signingIn": "Signing in…", "signOut": "Sign out", "invalid": "Invalid email or password", "networkError": "Could not reach the server", "sessionExpired": "Your session expired — please sign in again.", "signingOut": "Signing out…" },
   "objects": { "title": "Objects", "empty": "No objects yet", "loadError": "Could not load objects", "notFound": "Object not found", "prev": "Previous", "next": "Next", "of": "of", "new": "New object", "filter": "Filter objects…", "pageSize": "Per page", "columns": { "number": "Object №", "name": "Name", "visibility": "Visibility", "location": "Location", "count": "#", "updated": "Updated" }, "unknownRef": "(unknown)", "detailTitle": "Object detail", "tableLabel": "Objects" },
   "fieldsLabels": { "objectNumber": "Object number", "objectName": "Name", "count": "Number of objects", "briefDescription": "Brief description", "currentLocation": "Current location", "currentOwner": "Current owner", "recorder": "Recorder", "recordingDate": "Recording date", "visibility": "Visibility" },
   "visibility": { "draft": "Draft", "internal": "Internal", "public": "Public" },
   "form": { "selectPlaceholder": "— select —", "create": "Create object", "save": "Save", "cancel": "Cancel", "visibility": "Visibility", "draft": "Draft", "internal": "Internal", "required": "This field is required", "rejected": "The server rejected the changes — check required and referenced fields", "fieldRejected": "The field \"{{field}}\" was rejected — check its value", "createdButFieldRejected": "Object created, but a field was rejected — fix it below.", "flexibleHeading": "Catalogue fields", "saving": "Saving…", "createAnother": "Save & create another", "minCount": "Must be at least 1", "fieldError": { "type_mismatch": "Wrong type for this field", "unresolved": "Referenced value not found", "unknown": "Unknown field" }, "unsaved": { "title": "Discard unsaved changes?", "body": "You have unsaved changes that will be lost.", "stay": "Keep editing", "leave": "Discard" } },
-  "actions": { "edit": "Edit", "delete": "Delete", "rename": "Rename", "save": "Save", "closeDetail": "Close detail", "confirmDelete": "Delete this object? This cannot be undone.", "confirmDeleteTerm": "Delete this term? This cannot be undone.", "confirmDeleteAuthority": "Delete this authority? This cannot be undone.", "confirmDeleteField": "Delete this field definition? This cannot be undone.", "confirmDeleteVocabulary": "Delete this vocabulary? This cannot be undone.", "inUse": "Can't delete — used by {{count}} object(s). Clear those fields first." },
+  "actions": { "deleting": "Deleting…", "edit": "Edit", "delete": "Delete", "rename": "Rename", "save": "Save", "closeDetail": "Close detail", "confirmDelete": "Delete this object? This cannot be undone.", "confirmDeleteTerm": "Delete this term? This cannot be undone.", "confirmDeleteAuthority": "Delete this authority? This cannot be undone.", "confirmDeleteField": "Delete this field definition? This cannot be undone.", "confirmDeleteVocabulary": "Delete this vocabulary? This cannot be undone.", "inUse": "Can't delete — used by {{count}} object(s). Clear those fields first." },
   "labels": { "label": "Label", "externalUri": "External URI (optional)", "otherLanguages": "This entry also has labels in other languages, which are kept.", "uriPlaceholder": "https://…" },
   "theme": { "light": "Light", "dark": "Dark", "system": "System" },
   "vocab": {