fix: populate keyTrends in AI insights was always returning empty array

[ayuxsh009]

Description

This PR fixes an issue where the keyTrends array in generateAIInsights (src/lib/ai.ts) was always returned as an empty array.

Although the function generated values for achievements, areasOfConcern, and recommendations, no logic existed to populate keyTrends, causing the “Key Trends” section in the UI to remain permanently blank.

This update adds meaningful trend insights derived from existing analytics data and removes duplicate calculations to improve maintainability.

Fixes #78

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Changes

• Fix
• Populated keyTrends with real analytical insights
• Added week-over-week contribution trend analysis
• Added engagement rate and NPS trend reporting
• Added tech partner collaboration metrics
• Added issue completion trend summaries
• Added contributor activity trend insights
• Removed duplicate latestIssues and completionRate calculations
• Refactored shared analytics computation logic

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📷 Screenshots / Demo (if applicable)

N/A — backend AI insight generation fix.

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🔍 Additional Notes

Problem

keyTrends was initialized but never populated:

const keyTrends: string[] = [];

As a result:

• The Key Trends UI section always appeared empty
• The returned AIInsights object was incomplete
• Consumers could incorrectly assume no trends existed

Solution

This PR now generates 6 factual trend observations using existing analytics data already available in the function, including:

• Week-over-week contribution movement
• Engagement rate analysis
• Program NPS score trends
• Active tech partner collaboration
• Issue completion metrics
• Contributor activity summaries

Refactor

Duplicate calculations for:

• latestIssues
• completionRate

were consolidated into shared computations to avoid redundant processing and improve readability.

Files Changed

• src/lib/ai.ts (modified)

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Checklist

• I have tested this code
• I have added necessary documentation
• I have linked relevant issue(s)
• I followed the code style of the project
• I reviewed my own code

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