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/components/EmptyState.tsx

@@ -1,3 +1,4 @@
+import { Plus } from "lucide-react";
 import type { LucideIcon } from "lucide-react";
 import { Button } from "@/components/ui/button";
 
@@ -11,10 +12,13 @@ interface EmptyStateProps {
 export function EmptyState({ icon: Icon, message, action, onAction }: EmptyStateProps) {
   return (
     <div className="flex flex-col items-center justify-center py-16 text-center">
-      <Icon className="h-12 w-12 text-muted-foreground/50 mb-4" />
+      <div className="rounded-xl bg-muted/50 p-4 mb-4">
+        <Icon className="h-10 w-10 text-muted-foreground/50" />
+      </div>
       <p className="text-sm text-muted-foreground mb-4">{message}</p>
       {action && onAction && (
-        <Button variant="outline" size="sm" onClick={onAction}>
+        <Button onClick={onAction}>
+          <Plus className="h-4 w-4 mr-1.5" />
           {action}
         </Button>
       )}