Improves leaderboard performance with caching

[jhheider]

Adds a caching layer to the leaderboard endpoint to reduce database load and improve response times. The cache stores project data and invalidates entries after a configurable time-to-live (TTL). Fetches missing projects from the database and updates the cache. Increments API version.

This reduces 100-package query time from 158s to 85ms (around a 2000x improvement) for local queries across the tunnel.

[Copilot]

Pull Request Overview

This PR implements a caching layer for the leaderboard endpoint to significantly improve performance by reducing database load. The cache stores project data with a 1-hour TTL and fetches only missing projects from the database.

Key changes:

• Added project caching infrastructure with TTL-based expiration
• Modified leaderboard logic to check cache first, then query database for missing projects
• Incremented API version from 1.2.1 to 1.3.0

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
api/src/app_state.rs	Adds ProjectCacheEntry struct and cache field to AppState
api/src/main.rs	Initializes project cache in application startup
api/src/utils.rs	Adds helper function to retrieve cached projects and identify missing ones
api/src/handlers.rs	Updates leaderboard endpoint to use caching logic with fallback to database
api/Cargo.toml	Adds dashmap dependency and increments version

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