perf: convert large PNG screenshots to WebP, fix Lighthouse job summary crash

- Convert tvos-pause.png (516KB→27KB), tvos-sources.png (514KB→41KB),
  tvos-settings.png (72KB→15KB), iphone3-emu.png (191KB→38KB) to WebP
- Update page.tsx imports to use .webp variants
- Fix site-audit Lighthouse "Write job summary" step crashing with exit 1
  when no report URL is available (&&-chain with set -e; use if/fi instead)

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

Author: JoeMatt

.github/workflows/site-audit.yml

@@ -237,7 +237,10 @@ jobs:
           echo "| Best Practices | ${B:-–} | $(score_icon $B 80) |" >> $GITHUB_STEP_SUMMARY
           echo "| SEO            | ${S:-–} | $(score_icon $S 90) |" >> $GITHUB_STEP_SUMMARY
           URL="${{ steps.scores.outputs.report_url }}"
-          [ -n "$URL" ] && echo "" >> $GITHUB_STEP_SUMMARY && echo "[View full Lighthouse report]($URL)" >> $GITHUB_STEP_SUMMARY
+          if [ -n "$URL" ]; then
+            echo "" >> $GITHUB_STEP_SUMMARY
+            echo "[View full Lighthouse report]($URL)" >> $GITHUB_STEP_SUMMARY
+          fi
 
   # ──────────────────────────────────────────────────────────
   # Security Scan — main / schedule / dispatch only

src/app/page.tsx

@@ -2,7 +2,7 @@ import type { Metadata } from 'next';
 import Image from 'next/image';
 import iphone1 from '@/images/screenshots/ios/iphone1-library.jpg';
 import iphone2 from '@/images/screenshots/ios/iphone2-search.jpg';
-import iphone3 from '@/images/screenshots/ios/iphone3-emu.png';
+import iphone3 from '@/images/screenshots/ios/iphone3-emu.webp';
 import ipad1 from '@/images/screenshots/ipad/ipad1-library.jpg';
 import ipad2 from '@/images/screenshots/ipad/ipad2-search.jpg';
 
@@ -14,9 +14,9 @@ export const metadata: Metadata = {
 import DownloadSection from '@/components/DownloadSection';
 import SocialButton, { DiscordIcon, XIcon, BmcIcon, PatreonIcon } from '@/components/SocialButton';
 import Features from '@/components/Features';
-import tvos1 from '@/images/screenshots/tvos/tvos-pause.png';
-import tvos2 from '@/images/screenshots/tvos/tvos-settings.png';
-import tvos3 from '@/images/screenshots/tvos/tvos-sources.png';
+import tvos1 from '@/images/screenshots/tvos/tvos-pause.webp';
+import tvos2 from '@/images/screenshots/tvos/tvos-settings.webp';
+import tvos3 from '@/images/screenshots/tvos/tvos-sources.webp';
 
 export default function Home() {
   return (