feat: add light/dark theme toggle with localStorage persistence

[MkDev11]

Summary

Adds a fully functional light/dark theme toggle to Gittensor UI with localStorage persistence. The entire application — including all charts, tables, diff viewers, code browsers, and layout components — has been updated to be theme-aware, replacing ~200+ hardcoded dark-mode colors with conditional palette tokens and alpha() calls. A new ThemeContext provider manages theme state globally, and a toggle button is available in the sidebar.

Key changes:

• ThemeContext — new React context + provider that wraps the app, exposes toggleTheme(), and persists the user's preference to localStorage
• theme.ts — fully dual-mode MUI theme with custom palette extensions (surface, border, status, diff) for both light and dark modes
• Layout — sidebar and app bar logos switch to solid black (brightness(0) CSS filter) in light mode
• Dashboard — PRStatusChart, KpiCard, CommitTrendChart, ContributionHeatmap, LiveCommitLog, RepositoriesTable, TierPerformanceTable, GlobalActivity, TierRepoCard all updated
• Leaderboard — LeaderboardCharts, TopPRsTable, TopRepositoriesTable, TopMinersTable, MinerCard, LeaderboardSidebar, SectionCard, MinerSection ECharts options and table styles updated
• PR detail views — PRFilesChanged split/unified diff views use opaque sticky line-number backgrounds, theme-aware borders/text; PRComments markdown body + timeline colors; PRDetailsCard, PRHeader updated
• Repository pages — CodeViewer, ReadmeViewer, ContributingViewer, RepositoryCodeBrowser, FileExplorer, LanguageWeightsTable, RepositoryWeightsTable, RepositoryScoreCard, RepositoryPRsTable, RepositoryIssuesTable, RepositoryContributorsTable, RepositoryCheckTab updated
• Other — HomePage, AboutPage, OnboardPage, IssuesPage, GettingStarted, Scoring, RoadmapContent, FAQ, BountyProgress, IssueHeaderCard, IssueSubmissionsTable, IssuesList, CredibilityChart, PerformanceRadar updated
• Tests — new theme.test.ts validating palette structure for both modes

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Demo Video

https://www.dropbox.com/scl/fi/c90qlvgztmrtzlz2vbz4t/screen-capture.webm?rlkey=qvoaseatuf8pwvlk698he2ozh&st=1bxa2q3g&dl=0

Checklist

• New components are modularized/separated where sensible
• Uses predefined theme (e.g. no hardcoded colors)
• Responsive/mobile checked
• Tested against the test API
• npm run format and npm run lint:fix have been run
• npm run build passes
• Screenshots included for any UI/visual changes

[MkDev11]

@anderdc @LandynDev can you please review the PR and let me know your feedback?

[MkDev11]

if you can see some of the cards are wrong color in the demo video, just ignore it. its already fixed
background and card are the same color

[anderdc]

howdy MK, although I like the quality of the PR, we're simply not looking for light/dark theme, our current theme suits us well and we prefer having it how it is now. Please feel free to make other PRs or perhaps start an issue thread/discussion if you're unclear on if something will work out

[anderdc]

closing

[travellingsoldier85]

Great work on this PR @MkDev11! The implementation looks solid — localStorage persistence for theme preference is the right approach, and updating 200+ hardcoded colors is no small effort. Even though the maintainers aren't prioritizing this right now, the quality here speaks for itself. Would love to see this revisited in a future release. 👍

[MkDev11]

Great work on this PR @MkDev11! The implementation looks solid — localStorage persistence for theme preference is the right approach, and updating 200+ hardcoded colors is no small effort. Even though the maintainers aren't prioritizing this right now, the quality here speaks for itself. Would love to see this revisited in a future release. 👍

Thanks for your feedback @travellingsoldier85

[James-4u]

I also feel like this pr is good enough and @anderdc already said he likes it.
Having this pr closed would affect final scoring I guess and I believe it's not fair enough as we already do collestral scoring, right?
I believe you guys can keep it open and merge when you feel like you need this feature.