AppImage catalog review: app starts dark on light systems (pre-paint default) #72

Summary

AppImageHub catalog review (PR #10929) flagged that Kensaku launches in a dark theme even on a light-mode test system. The reviewer asked "Why do we get dark mode?"

Root cause

index.html ships with a hardcoded data-theme="dark" so the UI is never unstyled before React mounts. On a fresh install, src/hooks/useTheme.ts swaps it to the OS preference (prefers-color-scheme) once get_config resolves, but the screenshot/first frame can be captured during that initial paint, before the swap lands — so it reads as dark.

Existing installs keep their saved theme (config is the durable source); fresh installs already follow the OS via systemTheme().

Fix

• Remove the hardcoded dark initial attribute in index.html (or resolve the theme before paint via an inline script reading prefers-color-scheme), so even the first frame matches the OS.
• Keep default_theme() in src-tauri/src/config.rs consistent (or document that the frontend owns first-run resolution).

Related (optional, from same review)

• Add AppStream metadata (usr/share/metainfo/com.gochi.kensaku.metainfo.xml) with a controlled screenshot.
• Embed update info (.zsync) so AppImageUpdate works (createUpdaterArtifacts is currently false).

Acceptance

• Fresh launch on a light system shows light mode from the first frame.
• Re-run AppImageHub test (/retest) passes without the "mostly dark" warning.