feat(a11y): WCAG 2.2 AA accessibility compliance (#209)

* feat(a11y): add i18n keys for ARIA labels and screen reader text

* fix(security): harden API against pentest findings

- Default TRUST_PROXY=false to prevent XFF rate limit bypass (PT-01)
- Return 400 instead of 500 on malformed JSON input (PT-03)
- Default MAX_PIPELINE_STEPS=20 to prevent DoS (PT-04)
- Validate clientJobId length (max 128) across all routes (PT-06)
- Add security headers to all reply.hijack() streaming responses (PT-07)
- Sanitize usernames in audit log to prevent stored XSS (PT-08)
- Block TRACE method with 405 response (PT-10)
- Add 429 RateLimited response to OpenAPI spec (PT-12)
- Default MAX_SVG_SIZE_MB=50 to limit SVGZ decompression (PT-13)
- Pin Dockerfile base images by digest
- Sanitize OIDC IdP error and sub claim in audit log
- Sync Docker compose/Dockerfile defaults with env.ts

* feat(a11y): convert all hardcoded aria-labels to i18n keys

Replace 49 hardcoded aria-label="..." strings across 25 files with
their corresponding t.a11y.* and t.common.* i18n references. Add
useTranslation import and hook call to 15 components that lacked it.
Zero hardcoded aria-labels remain in the codebase.

* feat(a11y): add aria-labels to icon-only buttons, aria-hidden on decorative icons, sr-only status text

* feat(a11y): add aria-live regions for processing status announcements

* feat(a11y): add skip-nav link, route announcer, main content landmark, and page h1 elements

* feat(a11y): add prefers-reduced-motion support, preserve functional spinners

* feat(a11y): add useFocusTrap hook for modal focus management

* feat(a11y): add focus trapping and dialog roles to all modals

* feat(a11y): add toggle switch roles, form labels, and error association

* fix(a11y): fix contrast failures, touch targets, and add nav landmark to sidebar

* fix(a11y): add role=switch to remaining toggle buttons found in verification sweep

apps/web/src/components/common/progress-card.tsx

@@ -22,7 +22,11 @@ export function ProgressCard({ active, phase, label, stage, percent, elapsed }:
   const sublabel = [stage, `${elapsed}s`].filter(Boolean).join(" · ");
 
   return (
-    <div className="bg-muted/80 border border-border rounded-xl p-3 space-y-2.5">
+    <div
+      role="status"
+      aria-live="polite"
+      className="bg-muted/80 border border-border rounded-xl p-3 space-y-2.5"
+    >
       <div className="flex items-center gap-2.5">
         <div className="w-8 h-8 rounded-lg bg-primary/10 flex items-center justify-center shrink-0">
           {icon}