feat: add unified usage popover with Claude and Codex tabs

- Created combined UsagePopover component with tab switching between providers
- Added Codex usage API endpoint and service (returns not available message)
- Updated BoardHeader to show single usage button for both providers
- Enhanced type definitions for Codex usage with primary/secondary rate limits
- Wired up Codex usage API in HTTP client

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/ui/src/store/app-store.ts

@@ -646,20 +646,24 @@ export interface CodexRateLimitWindow {
   limit: number;
   used: number;
   remaining: number;
-  window: number; // Duration in minutes
+  usedPercent: number; // Percentage used (0-100)
+  windowDurationMins: number; // Duration in minutes
   resetsAt: number; // Unix timestamp in seconds
 }
 
 export interface CodexUsage {
-  planType: CodexPlanType | null;
-  credits: CodexCreditsSnapshot | null;
   rateLimits: {
-    session?: CodexRateLimitWindow;
-    weekly?: CodexRateLimitWindow;
+    primary?: CodexRateLimitWindow;
+    secondary?: CodexRateLimitWindow;
+    credits?: CodexCreditsSnapshot;
+    planType?: CodexPlanType;
   } | null;
   lastUpdated: string;
 }
 
+// Response type for Codex usage API (can be success or error)
+export type CodexUsageResponse = CodexUsage | { error: string; message?: string };
+
 /**
  * Check if Claude usage is at its limit (any of: session >= 100%, weekly >= 100%, OR cost >= limit)
  * Returns true if any limit is reached, meaning auto mode should pause feature pickup.