### Changes
- Replace plan-based checks (`LOG_RETENTION`, `availableIn`) with
`useCheckEntitlements('log.retention_days')` in the chart interval
dropdown
- `ChartIntervalDropdown` now calls the entitlements hook internally
instead of receiving plan props
- Remove `LOG_RETENTION` constant and `availableIn` from
`CHART_INTERVALS`
- Update consumer components (`ProjectUsage`, `ProjectUsageSection`,
`ObservabilityOverview`) to remove plan prop passing
### Testing
- Head to `/project/_/observability` with a Free plan org.
- Click on the time selector "Last 7 days" is disabled, default is "Last
60 minutes", tooltip shows retention limit and upgrade link
<img width="827" height="151" alt="image"
src="https://github.com/user-attachments/assets/20988398-8f0a-46b6-be3d-af4e9d530f81"
/>
- With a Pro Org and above the "Last 7 days" option should be enabled
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Observability Dashboard: unified overview for service health and
database infrastructure with interactive charts and metric cards (CPU,
memory, disk I/O, connections, error rate, slow queries).
* Service Health Monitoring: per-service health cards and a
multi-service table with error/warning counts and drill-down links to
reports/logs.
* Interval Selector: new chart-interval dropdown with plan-aware
retention messaging.
* Menu & Reports: updated Observability menu with Overview entry and
Custom Reports management.
* **Documentation**
* Added a footer link to troubleshooting guides.
<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
