docs: add Self-hosted deprecation notice to chart pages [OD-245]

[claudiacodacy]

Adds a notice at the top of every /chart/ page saying Codacy Self-hosted is no longer available for new customers, with a "Talk to us" link (the start-chat link the docs use for upgrade prompts) for readers with specific requirements. Requested in OD-245.

What changed

• theme/partials/notices.html: new notice shown when page.url starts with chart/. These pages come from the codacy/chart submodule, so the theme renders the notice and the chart repo doesn't change. The notice reuses the existing docs-notice style, which already supports both color schemes.

Not covered

• The versioned Self-hosted sites (/v14.0/ and older) are built from release/v* branches, which use the old codacy-mkdocs-material theme. They keep their existing "This documentation applies to Codacy Self-hosted" notice. Changing that copy would mean updating that repo and redeploying each release branch. Those builds already send noindex.
• The notice is skipped on builds with MKDOCS_SELF_HOSTED set, since those builds already show a Self-hosted notice.

Checks

• mkdocs build --strict passes.
• The notice appears on all 22 real pages under site/chart/ and on no other page. The 23rd file there is a redirect stub.
• Looked at /chart/ and /chart/maintenance/upgrade/ at desktop width in light and dark mode, and at 375 px wide in light mode.

👀 Live preview

🚧 To do

• If relevant, include the Jira issue key at the end of the pull request title
• Perform a self-review of the changes
• Fix any issues reported by the CI/CD

🤖 Generated with Claude Code

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

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[codacy-production]

Pull Request Overview

✅ No blocking issues noticed

No blocking findings were identified. No acceptance-criteria gaps were reported by the review agents.

Test suggestions

• Render a chart page in a non-Self-hosted build and verify the deprecation notice and Quickstart link are present.
• Render a chart page in a Self-hosted build and verify the deprecation notice is absent.
• Render a non-chart page and verify the new notice is absent.

Prompt proposal for missing tests

Consider implementing these tests if applicable:
1. Render a chart page in a non-Self-hosted build and verify the deprecation notice and Quickstart link are present.
2. Render a chart page in a Self-hosted build and verify the deprecation notice is absent.
3. Render a non-chart page and verify the new notice is absent.

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