feat: implement GitHub contributions heatmap timestamps (#203)

[Adi-Marathe]

What does this PR do?

Fixes #203 by properly implementing precise timestamps for the GitHub Contributions heatmap grid on the user's profile page.

Description

• Real Dates Over Relative Dates: Updated the grid data population logic to parse exact GitHub contribution dates, replacing the fallback "days ago" relative strings.
• Fixed Grid Padding References: Repaired a bug that occurred for users with fewer than 16 weeks of data, where padded weeks were inadvertently sharing array references.
• Performance Optimizations: Heavily refactored the date and timestamp calculation mechanisms inside the grid generators (for both GitHub and Platform heatmaps) to instantiate Intl.DateTimeFormat outside of the nested loops. We're now generating strings strictly from performant millisecond timestamp arithmetic, bypassing hundreds of costly new Date() calls.
• Visual Accuracy: Maintained standard GitHub UI metrics where hovering over grid spots yields the precise commit count explicitly matched to their calendar dates (e.g. 5 commits on Oct 14, 2023).

Acceptance Criteria met:

• Renders a dedicated green GitHub Contributions grid with accurate data mapping
• Resolves previous mock data placeholder behaviors
• Hovering over a square now outputs precise commit counts mapped directly to their chronological timestamp.

Media

RankerHub-.-Gamified-Developer-Leaderboard.3.mp4

Closes: #203

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Project	Deployment	Actions	Updated (UTC)
ranker-hub	Ready	Preview, Comment	Jun 4, 2026 1:34pm