Comprehensive UX audit fixes: navigation, feedback, affordances, and accessibility

Address 18 issues across high/medium/low impact tiers identified in a full
interface review. Key changes: Models page decomposed into tabs, confirmation
dialogs for irreversible actions (deploy/open-source/acquire), chart Y-axes
made visible, hash router extended for Market tab persistence, collapsible
sidebar, keyboard navigation shortcuts (g+key chords), notification bulk
actions, achievement progress bars, and ARIA label improvements.

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

apps/web/src/pages/SettingsPage.tsx

@@ -83,14 +83,17 @@ export function SettingsPage() {
             <div className="text-sm">Music Volume</div>
             <div className="text-xs text-surface-400">Background music level</div>
           </div>
-          <input
-            type="range"
-            min={0}
-            max={100}
-            value={settings.musicVolume * 100}
-            onChange={(e) => setMusicVolume(Number(e.target.value) / 100)}
-            className="w-32 accent-accent"
-          />
+          <div className="flex items-center gap-2">
+            <input
+              type="range"
+              min={0}
+              max={100}
+              value={settings.musicVolume * 100}
+              onChange={(e) => setMusicVolume(Number(e.target.value) / 100)}
+              className="w-32 accent-accent"
+            />
+            <span className="text-sm font-mono text-surface-400 w-8 text-right">{Math.round(settings.musicVolume * 100)}%</span>
+          </div>
         </div>
       </div>