Live demo Grafana instance (grafana-lake.demo.devlake.io) is unreachable - all live demo links broken

## Description

The hosted Grafana instance at `grafana-lake.demo.devlake.io` appears to be completely down. All "View live metrics on Grafana" links across the website return no response — the server is unreachable at every endpoint (root, `/grafana/`, `/grafana/api/health`, individual dashboard URLs).

## Impact

This affects **every live demo page** on the website, as well as the homepage:

**Live demo pages** (under `livedemo/`):
- [DORA](https://devlake.apache.org/livedemo/EngineeringLeads/DORA/) — links to `grafana-lake.demo.devlake.io/grafana/d/qNo8_0M4z/dora`
- [Engineering Overview](https://devlake.apache.org/livedemo/EngineeringLeads/EngineeringOverview/)
- [Engineering Throughput and Cycle Time](https://devlake.apache.org/livedemo/EngineeringLeads/EngineeringThroughputAndCycleTime/)
- [Weekly Bug Retro](https://devlake.apache.org/livedemo/EngineeringLeads/WeeklyBugRetro/)
- [GitHub](https://devlake.apache.org/livedemo/DataSources/GitHub)
- [GitLab](https://devlake.apache.org/livedemo/DataSources/GitLab)
- [Jenkins](https://devlake.apache.org/livedemo/DataSources/Jenkins)
- [Jira](https://devlake.apache.org/livedemo/DataSources/Jira)
- [SonarQube](https://devlake.apache.org/livedemo/DataSources/SonarQube)
- [Weekly Community Retro](https://devlake.apache.org/livedemo/OSSMaintainers/WeeklyCommunityRetro/)
- [Community Experience](https://devlake.apache.org/livedemo/OSSMaintainers/CommunityExperience/)

**Homepage:**
- The "Top Community Contributors" section in [`src/components/Team/Contributor.tsx`](https://github.com/apache/incubator-devlake-website/blob/main/src/components/Team/Contributor.tsx#L92) embeds an iframe from `grafana-lake.demo.devlake.io`
- The "See Live Demo" link in [`src/components/Sections/WhyDevlake.tsx`](https://github.com/apache/incubator-devlake-website/blob/main/src/components/Sections/WhyDevlake.tsx#L151)

**DORA docs** (all versions from v0.15 through Next):
- Each version's `DORA.md` links to the live demo Grafana instance

## Current Behavior

Clicking any "View live metrics on Grafana" link results in a timeout / connection refused. The static screenshots (PNG) on each page still display, but the interactive Grafana links are all dead links.

## Expected Behavior

The Grafana links should either:
1. Point to a working hosted Grafana instance with live data, or
2. Be removed/replaced with a note if the hosted instance is no longer maintained

## Verified On

- Date: March 25, 2026
- Tested URLs: `https://grafana-lake.demo.devlake.io/`, `https://grafana-lake.demo.devlake.io/grafana/api/health`, `https://grafana-lake.demo.devlake.io/grafana/d/qNo8_0M4z/dora?orgId=1`
- All return connection failures