[codex] UI theme overhaul and version bump

[parthashirolkar]

Summary

This branch contains the UI theme overhaul work plus the follow-up auth icon and release metadata updates.

UI overhaul already present on the branch

• Reworks the frontend theme system around semantic theme tokens in frontend/src/index.css.
• Updates the main palette, settings, auth, vault health, password generator, credential modes, and shared UI components to use theme-aware colors, typography, borders, shadows, and spacing.
• Adds/updates theme handling for dark-focus, clean-light, win98, and accessible via frontend/src/hooks/useTheme.ts and startup theme application in frontend/src/main.tsx.
• Adds Google SVG assets and a local fingerprint SVG component for the auth UI.
• Adds/updates product documentation in PRODUCT.md.

Follow-up fixes from this session

• Fixes the biometric auth method card contrast in Settings by pairing selected card backgrounds with text-theme-accent-text so the icon/title remain visible across themes.
• Increases the biometric fingerprint icon size on the lock screen by 20% and in Settings by 10%.
• Bumps app version metadata from 0.2.4 to 0.2.5 in frontend/package.json, frontend/src-tauri/tauri.conf.json, and frontend/src-tauri/Cargo.toml.

Validation

• bun run typecheck
• cargo fmt --all -- --check
• cargo check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test

No forbidden build commands were run.

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