feat(org): add celebration confetti when joining or creating organization

Add a celebratory experience when users join or create an organization:
- Add canvas-confetti dependency for visual effects
- Store organization name in localStorage after successful join/create
- Display celebration dialog with confetti animation on ProfilePage
- Clear the celebration flag after showing to prevent repeat displays

src/pages/auth/OrgSetupPage.tsx

@@ -99,11 +99,14 @@ export default function OrgSetupPage() {
     setOrgSlug(value.toLowerCase().replace(/[^a-z0-9-]/g, ""));
   };
 
-  const done = async () => {
+  const done = async (orgName?: string) => {
     await refreshUser();
     await checkOrgAdmin();
     queryClient.invalidateQueries({ queryKey: ['organizations'] });
-    navigate("/profile", { replace: true });
+    if (orgName) {
+      localStorage.setItem('justJoinedOrg', orgName);
+    }
+    navigate('/profile', { replace: true });
   };
 
   // ── Accept an invite ───────────────────────────────────────────────────────
@@ -113,7 +116,7 @@ export default function OrgSetupPage() {
     try {
       const result = await api.invites.accept(invite.token);
       if (result.token) tokenManager.setToken(result.token, result.expires_at ?? null);
-      await done();
+      await done(invite.organization.name);
     } catch (err) {
       setJoinError(err instanceof ApiError ? err.message : "Failed to join organisation. Please try again.");
       setJoiningToken(null);
@@ -129,7 +132,7 @@ export default function OrgSetupPage() {
     setIsCreating(true);
     try {
       await api.organizations.create(orgName.trim(), orgSlug.trim());
-      await done();
+      await done(orgName.trim());
     } catch (err) {
       setCreateError(err instanceof ApiError ? err.message : "Failed to create organisation. Please try again.");
     } finally {