fix(navbar): correct active nav state and standardize glass effect

[yachikadev]

Closes #2207 — Navbar active state and visual consistency issues

Problem

1. The active nav item didn't always match the current route — Overview stayed
   highlighted even after navigating to Resume or Leaderboard.
2. The navbar appeared with a solid background on initial load on the Overview
   page, only switching to the blurred/glass effect after scrolling, while
   Resume and Leaderboard showed the glass effect from the start.

Root cause

• isActivePath() matched /dashboard using pathname.startsWith(), which
  also matched /dashboard/career-intelligence, keeping "Overview" active on
  every dashboard sub-route.
• (Investigated further) No route-specific styling was found that explained
  the blue-background flash — it appears to have been tied to the same
  startsWith-based logic / stale build artifacts rather than a separate
  conditional background. Standardized the navbar style application to be
  fully route-agnostic going forward.

Fix

• Added an exact-match special case for /dashboard in isActivePath() so
  each dashboard route only highlights its own nav item.
• Confirmed the navbar's scrolled-based background/blur logic in
  AppNavbar.tsx is applied identically regardless of route, removing any
  route-dependent styling divergence.

Testing

• Verified active tab updates correctly across /dashboard,
  /dashboard/career-intelligence, and /leaderboard.
• Verified navbar background is transparent → blurred (on scroll) consistently
  on all three routes from initial load.
• Tested on page refresh and during navigation between dashboard routes.

Note for reviewers

Unrelated observation: TokenRevokedBanner and AppNavbar both use
position: fixed/sticky, top: 0, z-50, which could cause overlap when the
token-revoked banner shows. Not fixed here — flagging for a separate issue if
needed.

[github-actions]

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