Polish UI: enhance dialogs, command palette, and page layouts

Expand NewIssueDialog with richer form fields. Add NewProjectDialog.
Enhance CommandPalette with more actions and search. Improve
CompanySwitcher, EmptyState, and IssueProperties. Flesh out Activity,
Companies, Dashboard, and Inbox pages with real content and layouts.
Refine sidebar, routing, and dialog context. CSS tweaks for dark theme.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/index.css

@@ -120,3 +120,8 @@
     @apply bg-background text-foreground;
   }
 }
+
+/* Expandable dialog transition for max-width changes */
+[data-slot="dialog-content"] {
+  transition: max-width 200ms cubic-bezier(0.16, 1, 0.3, 1);
+}