fix(web): accessibility pass to WCAG 2.1 AA (M7)

An axe-core audit of every screen in both themes found low contrast on white
text over the accent and on caption text, track rows using row roles without
cells, and unlabelled progress bars. Accent fills now use a darker token,
caption text meets 4.5:1, track lists are lists and progress bars are labelled.
The queue drawer slides in from the right as designed, takes focus, closes on
Escape and notes that the wave never ends.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/i18n/locales/en/common.json

@@ -81,7 +81,8 @@
     "source_wave": "My Wave",
     "source_queue": "Queue",
     "queue": "Queue",
-    "source_wave_seed": "Artist wave · {{label}}"
+    "source_wave_seed": "Artist wave · {{label}}",
+    "queue_wave": "The wave never ends: next tracks are picked as you listen"
   },
   "settings": {
     "title": "Settings",