chore: add codex audit reports

.codex/audits/frontend-performance-2026-07-03/fixes/03-image-asset-optimization.md

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+# Fix 03: optimize logo and icon assets
+
+Priority: P1  
+Risk: Low  
+Primary benefit: First-load transfer
+
+## Issue
+
+The navigation logo is a 1100x849 PNG weighing about 392KB, but it is displayed at roughly 40px high. The favicon is a 512x512 PNG weighing about 113KB. Their source dimensions and transfer sizes are much larger than their rendered use.
+
+These files are cached by the browser after first use, but the first authenticated page pays the cost. Without long-lived cache headers, they may also be revalidated more often than necessary.
+
+## Desired behavior
+
+- The navigation logo remains visually crisp on standard and high-density displays.
+- Transparency is preserved.
+- Favicons and Apple touch icons use purpose-sized files.
+- The application manifest references valid dimensions.
+- The total first-load logo/icon transfer is materially smaller.
+
+## Proposed asset set
+
+### Navigation logo
+
+Create a transparent asset around 128px high for a 40px CSS slot. This provides more than 3x density for high-DPI screens without shipping the 1100px source.
+
+Preferred formats:
+
+- WebP for the navigation image, with PNG fallback only if a target browser requires it.
+- Optimized PNG if keeping one format is operationally simpler.
+
+Do not use AVIF for a tiny UI logo unless the encoder preserves edges and transparency without visible artifacts; byte savings may not justify compatibility and build complexity.
+
+### Favicons
+
+Use purpose-sized files:
+
+- 32x32 and optionally 16x16 favicon.
+- 180x180 Apple touch icon.
+- 192x192 and 512x512 manifest icons if the PWA manifest advertises those sizes.
+
+The large manifest icon should not be loaded as the ordinary browser favicon.
+
+## Implementation steps
+
+1. Keep the original logo source outside the runtime asset path or clearly mark it as source artwork.
+2. Export the navigation logo at an appropriate high-density dimension.
+3. Export favicon/touch/manifest variants at their declared sizes.
+4. Update `templates/components/navigation.gohtml`, `templates/base.gohtml`, and `static/assets/manifest.json` to reference the correct variants.
+5. Add explicit `width` and `height` attributes to the navigation `<img>` to reserve layout space and avoid layout shift.
+6. Combine with immutable caching after filenames or URLs are versioned.
+
+## Quality checks
+
+Inspect assets against both light and dark themes:
+
+- No white or dark halo around transparent edges.
+- No visible ringing or color shift.
+- Logo remains legible at its actual 40px display size.
+- Touch icon background and mask behavior are intentional.
+- Browser tabs show the correct favicon at small sizes.
+
+## Affected files
+
+- `static/assets/logo.png` or its replacement
+- `static/assets/favicon.png` and icon variants
+- `static/assets/manifest.json`
+- `templates/base.gohtml`
+- `templates/components/navigation.gohtml`
+
+## Tests
+
+- Manifest JSON remains valid and every referenced file exists.
+- Declared icon dimensions match actual dimensions.
+- Template render tests include the intended logo/favicon URLs and explicit navigation-image dimensions.
+- Browser smoke test confirms logo and favicon requests return `200`.
+
+## Verification
+
+- Compare file sizes before and after.
+- Open home, login, and watch pages at 1x and 2x device scale.
+- Check the browser tab icon.
+- Inspect the manifest in browser developer tools.
+- Confirm image requests return the intended cache headers after Fix 02.
+
+## Observability
+
+Record asset byte sizes in the build/release output. Browser monitoring should watch image request failures and layout shift around navigation. No user-identifying telemetry is needed.
+
+## Rollout
+
+Ship new filenames or versioned URLs so old cached images cannot mask the result. Keep the previous source artwork outside the served runtime path for easy re-export, but do not retain oversized duplicates under URLs browsers may fetch.
+
+## Acceptance criteria
+
+- Navigation logo is below 50KB, preferably below 25KB.
+- Ordinary favicon is below 20KB.
+- No visible regression at the rendered size.
+- Explicit image dimensions prevent navigation layout shift.
+- Manifest icon declarations match actual pixel dimensions.