feat(generator): Enhance README customization with multiple layout templates

[Rakshak05]

Description

Fixes #7814

Added support for structural layout templates (Classic, Minimalist, Data Heavy, Storyteller) in readmeGenerator.ts and the README Editor UI, enabling users to customize the ordering of their profile sections.

Summary of Changes:

• Types & State: Defined LayoutTemplate ('classic' | 'minimalist' | 'data-heavy' | 'storyteller') in types.ts and added layoutTemplate to GeneratorState.
• Generator Core: Modularized section builders in readmeGenerator.ts and arranged sections dynamically according to the chosen template.
• UI Editor: Created the LayoutTemplateSection component in the editor sidebar with visual template badges and section order previews.
• Presets: Configured default PROFILE_PRESETS with matching layout templates.
• Test Coverage: Added dedicated unit tests in readmeGenerator.layout-templates.test.ts verifying section reordering across all templates.

Pillar

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

Visual Preview

(Optional: Attach a screenshot or GIF of the new Layout Template selector card from the generator UI)

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have starred the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

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[retenta-bot]

This pull request introduces multiple layout templates for the README generator, enhancing user customization options. It aligns with previous decisions to improve user experience, such as the addition of a dark/light preview background toggle. This feature will allow users to visualize their README in different contexts, similar to how the background toggle enhances the contribution graph embed preview. Great work on this! Looking forward to your contributions.

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[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

Asset	PR Size	Base Size	Difference	Status
static/chunks/app/generator/page-[hash].js	37.76 KB	36.59 KB	+1.17 KB (+3.21%)	🔴 Regression
static/css/[hash].css	43.63 KB	43.55 KB	+0.08 KB (+0.18%)	🔴 Regression

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	5002.89 KB	4998.89 KB	+4.00 KB (+0.08%)
Total CSS	355.00 KB	354.18 KB	+0.82 KB (+0.23%)