Add start and end date to weekly project statistics

[wroug]

Summary of the problem

Creating this for #1604
Closes #1605

Describe your changes

Allow callers to get weekly project stats for custom date ranges, not only 12 weeks before today.

• weekly_project_stats and week_ranges now accept optional start_date and end_date parameters

[greptile-apps]

Greptile Summary

The PR adds optional start and end dates to weekly project aggregation and changes weekly bucket generation.

• Converts requested boundaries into the user's timezone before querying heartbeats
• Generates weekly buckets across custom ranges
• Attempts to preserve the original twelve-week default window

Confidence Score: 4/5

The PR is not yet safe to merge because the default weekly aggregation still returns inconsistent bucket counts between live and rollup-backed paths.

The attempted default-window fix is bypassed when weekly_project_stats passes its internally derived effective_start as an explicit start_date, leaving live aggregation and rollup generation at thirteen buckets while rollup reads expose twelve.

Files Needing Attention: app/services/dashboard_data/snapshots.rb

Important Files Changed

Filename	Overview
app/services/dashboard_data/snapshots.rb	Adds custom weekly date ranges, but the default live aggregation still bypasses the corrected twelve-bucket branch and diverges from rollup reads.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[weekly_project_stats without dates] --> B[Derive effective_start]
  B --> C[Pass effective_start as start_date]
  C --> D[week_ranges custom branch]
  D --> E[13 generated buckets]
  E --> F[Live result and rollup refresh]
  G[Rollup reader] --> H[week_ranges without dates]
  H --> I[12 generated buckets]

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Prompt To Fix All With AI

### Issue 1
app/services/dashboard_data/snapshots.rb:89
**Default window still has thirteen buckets**

When `weekly_project_stats` is called without dates, it passes the derived `effective_start` as a supplied start date, causing `week_ranges` to select the custom-range branch and generate thirteen buckets. Live aggregation and rollup generation therefore cover thirteen weeks while rollup reads expose twelve, producing different weekly statistics depending on whether a valid rollup is available.

```suggestion
      ranges = week_ranges(user.timezone, start_date: start_date, end_date: end_date)
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (3): Last reviewed commit: "Merge branch 'main' into weekly-project-..." | Re-trigger Greptile}

[greptile-apps]

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[wroug]

truly amazing