test(dashboard): add comprehensive D1 integration tests for dashboard repository

[saifulalomdev]

📝 Description

This PR replaces the placeholder dashboard repository test file with a comprehensive integration test suite for dashboardRepository. It removes test mocking in favor of real database execution using Cloudflare D1 worker bindings and the Drizzle ORM schema instance.

The suite verifies:

• Aggregations for current vs. previous traffic stats, bounce rates, conversion rates, and session durations.
• Sorting and limit handling for pageviews, countries, and referrers.
• Screen width classification logic (Desktop, Tablet, Mobile).
• SQL recursive CTE bucket generation for time-series trends.

Fixes # (issue number)

🧪 Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor / Chore (codebase maintenance or optimization)

🛠️ How Has This Been Tested?

The test suite was executed locally utilizing native worker environments and secrets mapped from .dev.vars. All 6 integration specs run and pass cleanly in under 120ms.

• Unit/Integration tests added/passed
• Local manual edge verification successful

📸 Screenshots / Diffs (if applicable)

✓  server-workers  src/modules/dashboard/__tests__/dashboard.repository.test.ts (6 tests) 110ms

Test Files  1 passed (1)
     Tests  6 passed (6)

✅ Checklist

• My code follows the brutalist/minimal style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new typescript compiler or linter errors