fix(insights): keep usage windows on the viewer's local hour

[waleedlatif1]

Summary

• Partial custom range falls back to the current period without dropping the viewer's timezone, so an unbounded (self-hosted) period's trailing window starts on the local hour and its first segment can settle and cache
• The unbounded previous period now ends exactly where the current period's window starts, both ends on the viewer's hour — previously it was [now − 60d, now − 30d), which overlapped the current window by up to an hour and left two partial hours re-read on every view
• Extracted startOfLocalHour so both windows share one alignment rule

Type of Change

• Bug fix

Testing

• Regression tests for both paths (Asia/Kolkata, half-hour offset); both fail against the previous code
• Billing + Insights suites incl. real-Postgres: 1,187 passed
• Lint, type-check, check:audits, docs-manifest, block registry all green

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 23, 2026 3:52pm UTC

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with the changed window boundaries matching existing half-open query and local-hour segment contracts.

Summary

This PR consistently aligns unbounded usage windows to the viewer’s local hour.

• Preserves the supplied timezone when an incomplete custom range falls back to the current period.
• Makes unbounded previous and current windows adjacent under the existing half-open range semantics.
• Extracts the shared local-hour alignment logic and adds regression coverage using a half-hour-offset timezone.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  N[Current instant] --> C[Align now - 30 days to viewer-local hour]
  C --> CW["Current window: [current.from, now)"]
  C --> P[Subtract another 30 days and align]
  P --> PW["Previous window: [previous.from, current.from)"]

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_{Reviews (1) · Last reviewed commit: "fix(insights): keep usage windows on the..."}

[cubic-dev-ai]

All reported issues were addressed across 2 files

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>