feat(canvas): add shared workspace access and controls

frontend/src/i18n/locales/en-US.json

@@ -111,6 +111,41 @@
   "share": "Share",
   "shareLinkCopied": "Share link copied",
   "shareUnavailable": "Sharing is unavailable",
+  "shareDesign": "Share design",
+  "sharePeopleWithAccess": "People with access",
+  "shareAddPeople": "Add people",
+  "shareVisitorCount": "{count} visitors",
+  "shareVisitors": "Visitors",
+  "shareAccessLevel": "Access level",
+  "shareAnyoneWithLink": "Anyone with the link",
+  "shareLinkPermission": "Link permission",
+  "sharePrivate": "Private",
+  "shareCanvasOnly": "Canvas only",
+  "shareCanView": "Can view",
+  "shareCanEdit": "Can edit",
+  "sharePrivateHint": "Only invited people can access",
+  "shareCanvasHint": "Shows only the canvas without chat or editing tools",
+  "shareViewerHint": "Can view the canvas and chat, but cannot edit",
+  "shareEditorHint": "Sign-in is required before editing",
+  "shareCopyLink": "Copy link",
+  "shareEmail": "Email",
+  "shareReadOnlyLink": "Shared link",
+  "shareViewerCopyHint": "You can copy and forward this shared link.",
+  "shareInvitePlaceholder": "Add an email address or phone number",
+  "shareInvite": "Invite",
+  "shareInviteAdded": "Person added",
+  "shareOwner": "Owner",
+  "shareNoVisitors": "No visitors yet.",
+  "shareAnonymousVisitor": "Anonymous visitor",
+  "shareRemoveAllTitle": "Remove access for everyone",
+  "shareRemoveAllDescription": "Remove everyone with access and make the design private. The old share link will stop working immediately.",
+  "shareRemoveAccess": "Remove access",
+  "shareConfirmRemove": "Confirm removal",
+  "shareAccessRemoved": "All shared access was removed",
+  "shareSettingsLoadError": "Could not load sharing settings",
+  "shareVisitorsLoadError": "Could not load visitors",
+  "shareUpdateError": "Could not update sharing settings",
+  "remove": "Remove",
   "download": "Download",
   "generate": "Generate",
   "more": "More",
@@ -466,6 +501,8 @@
   "messages.auth.provider_not_ready": "This sign-in service is not configured yet. Please try again later.",
   "messages.auth.human_verification_required": "Please complete the security check first.",
   "messages.auth.human_verification_failed": "Security check failed. Please verify again and retry.",
+  "messages.share.self_invite": "You already own this design and cannot invite yourself.",
+  "messages.share.member_exists": "This email address or phone number already has access.",
   "agentError.title.image": "Image generation did not complete",
   "agentError.title.partialImage": "Some images did not complete",
   "agentError.title.imageAction": "Image processing did not complete",