Implement nightly puzzle analytics rollup job

[phertyameen]

Description

Add a @Cron job that aggregates the previous day's puzzle attempts/completions into PuzzleAnalytics rows.

Why this matters

Puzzle-level completion rate and average solve time providers should read from pre-aggregated data rather than scanning raw events.

Files to touch

• backend/src/analytics/jobs/puzzle-analytics-rollup.job.ts

Acceptance Criteria

• Job correctly aggregates attempts, completions, and average time
• Job handles puzzles with zero attempts for the day gracefully

Notes

This issue is part of the new analytics module effort (tracking, aggregation,
and reporting on player/game activity). Please keep new code inside
backend/src/analytics/ following the same module/controller/service/provider
layout used by existing modules (e.g. progress, streak, quests).

[Samaro1]

gm gm boss, I would love to work on this issue. A satisfactory and efficient PR will be raised in 12 hours