fix: impersonation logout, applicant learning hub redirect, nav click tracking

- Sign Out button during impersonation now returns to admin instead of
  destroying the session (fixes multi-click logout issue)
- Applicant nav now respects learning_hub_external setting like jury/mentor
- Track Learning Hub nav clicks via audit log (LEARNING_HUB_CLICK action)

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

src/server/routers/learningResource.ts

@@ -271,6 +271,24 @@ export const learningResourceRouter = router({
       return { success: true }
     }),
 
+  /**
+   * Log when a user clicks the Learning Hub nav link (especially external).
+   * Creates an audit log entry so admins can see who accessed it.
+   */
+  logNavClick: protectedProcedure
+    .input(z.object({ url: z.string() }))
+    .mutation(async ({ ctx, input }) => {
+      await ctx.prisma.auditLog.create({
+        data: {
+          userId: ctx.user.id,
+          action: 'LEARNING_HUB_CLICK',
+          entityType: 'LearningResource',
+          detailsJson: { url: input.url, role: ctx.user.role },
+        },
+      }).catch(() => {})
+      return { success: true }
+    }),
+
   /**
    * Create a new resource (admin only)
    */