fix(themes): normalize theme query parameter lookup to make theme selection case-insensitive

[ChetanSenta]

Description

Fixes #6143

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix)

Visual Preview

No visual changes to the themes themselves. However, passing parameters like ?theme=CYANPULSE or ?theme=cyanpulse will now correctly load the cyanPulse theme style instead of crashing or breaking back to an unstyled fallback default state.

What this PR does

Previously, the incoming theme query parameter string was matched exactly against keys of the THEMES object. This meant strict case sensitivity was expected from end-users (cyanPulse worked, but cyanpulse or uppercase equivalents failed).

This PR introduces a getNormalizedThemeKey() utility inside lib/svg/themes.ts to scan and safely match theme names case-insensitively.

Changes

File	Change
lib/svg/themes.ts	Added getNormalizedThemeKey() case-insensitive lookup helper.
app/api/streak/route.ts	Updated the API route handler to pass query input through the new safe resolver.
lib/svg/themes.test.ts	Added 3 unit tests verifying lowercase, uppercase, and non-existent fallback handling.

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally.
• I have run npm run format and npm run lint locally and resolved all errors.
• My commits follow the Conventional Commits format.
• My branch has only one clean commit to merge.

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[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	3694.34 KB	3694.34 KB	0 B
Total CSS	296.06 KB	296.06 KB	0 B

[Aamod-Dev]

Excellent fix to improve user experience. Normalizing the theme query parameter using getNormalizedThemeKey in lib/svg/themes.ts prevents unnecessary fallbacks when users make minor casing typos. The logic in app/api/streak/route.ts elegantly integrates this helper. Approved!