Add system-wide policies info to README, docs introduction, and website homepage

[Copilot]

Changes proposed in this pull request

• Add system-wide policies mention to README.md enterprise-ready paragraph and bullet point (with link to docs)
• Add new "System-Wide Policies" section to docs/introduction.mdx below "Groups and Profiles"
• Update website homepage "Effortless Troubleshooting" feature card to mention system-wide policies

Related issue(s)

Follow-up to PR #3313 and #3324 — surfaces the new policy feature in user-facing docs.

Copilot generated summary

Copilot summary

Adds references to the system-wide policies feature (introduced via config.json for centralized enterprise configuration) across the three main entry points users encounter: the GitHub README, the documentation introduction page, and the website homepage feature cards.

To-Do

• Update documentation to reflect this changes
• Update changelog to reflect this changes

Contributing

By submitting this pull request, I confirm the following:

• I have read and understood the contributing guidelines and the code of conduct.
• I have have added my name, username or email to the contributors list or don't want to.
• The code or resource is compatible with the GNU General Public License v3.0.

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