test: add tests for progress dashboard (UserProfile, badges, streak, API)

[mohityadav8]

🧪 Overview

This PR adds comprehensive test coverage for the Progress Dashboard feature.

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✅ Tests Added

🧑‍💻 UserProfile Model

• XP → level calculation
• XP progress percentage
• Level boundaries (0, 99, 100, 200, 500, etc.)

🏅 Badge System

• Badge assignment correctness
• Badge filtering (unknown keys ignored safely)
• Badge metadata validation

🔥 Streak Logic (Signals)

• First login initializes streak
• Consecutive login increments streak
• Same-day login does not increment
• Missing profile is auto-created via signal

📊 Progress API

• Correct counts:
  • solved
  • in_progress
  • not_started
• XP and streak returned correctly in response

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🎯 Purpose

• Ensure correctness of progress tracking system
• Prevent regressions in XP, streak, and badge logic
• Improve overall test coverage for dashboard-related features

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📌 Notes

• Tests are isolated and do not modify existing logic
• No production code changes included in this PR
• All tests pass locally

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✅ Status

• All tests passing
• Ready for review