feat: add light/dark mode toggle

[andrewhopper]

Adds a light/dark mode toggle to the QuickView UI.

• Light mode CSS variables (shadcn/ui tokens) as a .light class
• Toggle button (☀️/🌙) in the header
• Persists preference in localStorage, falls back to system preference

Closes #25

Generated with Claude Code

[andrewhopper]

@claude fix the conflicts

[claude]

Claude finished @andrewhopper's task in 6m 41s —— View job

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Conflicts Fixed

• Gather context and understand request
• Check current conflict state
• Read CLAUDE.md for repo guidelines
• Apply light/dark mode changes to master's new file versions
• Commit and push resolved changes

What was done:

The conflicts were caused by PR #35 merging a completely restructured version of the frontend (modular ES6 with imports) while this PR still had the old monolithic architecture.

Resolution (1ecb30a):

• app.js: Ported to the new modular ES6 architecture from master, adding setupTheme() and applyTheme() methods to the new QuickViewApp class structure. setupTheme() is now called in the constructor before other setup.
• index.html: The theme toggle button was already present; fixed the <script> tag to use type="module" since the new app.js uses ES6 imports (this is required for modules to work).
• style.css: Already had the correct .light class variables — no changes needed.
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[andrewhopper]

@claude - resolve the conflicts

[claude]

Claude finished @andrewhopper's task in 4m 28s —— View job

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Conflict Analysis Complete

• Gather context and check current branch state
• Read CLAUDE.md for repo guidelines
• Identify conflicts and root cause
• Resolve conflicts (see instructions below)

What's Happening

The PR branch (claude/issue-25-20260303-1347) and master have no common ancestor — they are completely unrelated histories. This happened because PR #53 introduced a full TypeScript/React rewrite of the app, creating a fresh git history that doesn't connect to this PR's older history.

Good news: master already has the dark mode feature fully implemented:

• quickview-tool/src/client/hooks/useTheme.ts — dark/light mode logic with localStorage persistence
• quickview-tool/src/client/components/Header.tsx — Sun/Moon toggle button (☀️/🌙)
• quickview-tool/src/client/index.css — dark mode CSS variables

To Resolve

The git merge --allow-unrelated-histories command requires interactive approval that isn't available in CI. Run these commands locally:

git fetch origin
git checkout claude/issue-25-20260303-1347
git merge origin/master --allow-unrelated-histories -m "chore: resolve conflicts by merging master TypeScript rewrite"
git push origin claude/issue-25-20260303-1347

This will combine both histories and make the PR mergeable. Since master already has dark mode implemented, the PR effectively adds no new code changes — the feature is already in master via useTheme.ts.

Alternative: Since the feature is already in master, you could simply close this PR as superseded by #53.