feat: add comprehensive graphs module documentation

[Srishti-Gupta74]

Related Issue

Related to #13

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Description

Added comprehensive documentation for Module VI: Graphs.

Changes Made

• Added graph fundamentals and terminology
• Added graph types and classifications
• Added adjacency matrix and adjacency list representations
• Added BFS and DFS concepts, algorithms, and implementations
• Added complexity analysis and comparison sections
• Added applications, real-world examples, advantages, and limitations
• Added summary and interview questions
• Updated the contents page to include Graphs module topics

Additionally, the course contents page was updated to reflect the newly added Graphs module topics.

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Type of Change

• Bug fix
• New feature
• Documentation update
• UI/UX improvement
• Refactor

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Screenshots / Demo

Screenshots showing:

• The newly added Graphs module content

• Updated contents page with Module VI topics

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How Has This Been Tested?

• Verified the documentation structure locally.
• Reviewed all graph definitions, examples, algorithms, and complexity analyses for correctness.
• Checked formatting consistency with existing course modules.
• Confirmed the new chapter is accessible through the course navigation.

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Checklist

• My code follows the project structure and conventions
• I have tested the changes locally
• I have linked the related issue properly
• I have added screenshots where applicable
• No existing functionality was broken

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AI Usage

• I have not used AI tools for this contribution

• I have used AI tools (ChatGPT, Copilot, Claude, etc.) and I have reviewed, verified, and understood all generated code/content before submitting this PR

If AI tools were used, briefly explain how:

Used AI for fact-checking and reviewing documentation structure. All content was manually verified, edited, and adapted to match the project's documentation style before submission.

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Additional Notes

This PR completes the Graphs module documentation and maintains consistency with the structure and style of the existing Data Structures modules.

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