v0.2.0: WCAG 2.2 AAA accessibility + toggle fix + version bump

- Upgrade accessibility from WCAG 2.1 AA to WCAG 2.2 AAA conformance
- 42 accessibility fixes across 18 frontend components
- Enhanced contrast ratios (7:1 body text, 4.5:1 large text, 3:1 non-text)
- 44px minimum touch/click targets on all interactive elements
- Full WAI-ARIA 1.2: tablist, radiogroup, alertdialog, progressbar, switch
- Screen-reader-only data tables behind chart, dynamic page titles
- Skip navigation link, semantic heading hierarchy (h1 > h2)
- Celebration popups persist on hover/focus with keyboard dismiss
- Fix ToggleSwitch visual height (44px hit area, 28px visual track)
- Update README with detailed WCAG 2.2 AAA accessibility section
- Include WCAG design doc and implementation plan in docs/plans/

src-tauri/Cargo.lock

@@ -480,7 +480,7 @@ dependencies = [
 
 [[package]]
 name = "core-cooldown"
-version = "0.1.2"
+version = "0.2.0"
 dependencies = [
  "anyhow",
  "chrono",