feat(ui): add per-project themes and fix scrolling/styling issues

- Add per-project theme support with theme selector in sidebar
- Fix file diffs scrolling in agent output modal with proper overflow handling
- Improve cursor styling across all interactive elements (buttons, tabs, checkboxes)
- Enhance hotkey styling to use consistent theme colors
- Fix Kanban board flash/refresh issues with React.memo optimizations
- Update tab component for better theme integration with proper active states

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4 <noreply@anthropic.com>

app/src/components/ui/tabs.tsx

@@ -26,7 +26,7 @@ function TabsList({
     <TabsPrimitive.List
       data-slot="tabs-list"
       className={cn(
-        "bg-muted text-muted-foreground inline-flex h-9 w-fit items-center justify-center rounded-lg p-[3px]",
+        "bg-muted text-muted-foreground inline-flex h-9 w-fit items-center justify-center rounded-lg p-[3px] border border-border",
         className
       )}
       {...props}
@@ -42,7 +42,12 @@ function TabsTrigger({
     <TabsPrimitive.Trigger
       data-slot="tabs-trigger"
       className={cn(
-        "data-[state=active]:bg-background dark:data-[state=active]:text-foreground focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:outline-ring dark:data-[state=active]:border-input dark:data-[state=active]:bg-input/30 text-foreground dark:text-muted-foreground inline-flex h-[calc(100%-1px)] flex-1 items-center justify-center gap-1.5 rounded-md border border-transparent px-2 py-1 text-sm font-medium whitespace-nowrap transition-[color,box-shadow] focus-visible:ring-[3px] focus-visible:outline-1 disabled:pointer-events-none disabled:opacity-50 data-[state=active]:shadow-sm [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+        "inline-flex h-[calc(100%-1px)] flex-1 items-center justify-center gap-1.5 rounded-md border border-transparent px-2 py-1 text-sm font-medium whitespace-nowrap transition-all duration-200 cursor-pointer",
+        "text-foreground/70 hover:text-foreground hover:bg-accent",
+        "data-[state=active]:bg-primary data-[state=active]:text-primary-foreground data-[state=active]:shadow-md data-[state=active]:border-primary/50",
+        "focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:outline-ring focus-visible:ring-[3px] focus-visible:outline-1",
+        "disabled:pointer-events-none disabled:opacity-50 disabled:cursor-not-allowed",
+        "[&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
         className
       )}
       {...props}