docs: Create Administration and Security menu section

[guiwrite]

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Changes

• Create Administration and Security menu section with its subsections
• Move and adjust existing content to new folders
• Adjust structure of how-to guides

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 31, 2025 6:31pm

[vercel]

@guiwrite is attempting to deploy a commit to the Flagsmith Team on Vercel.

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[matthewelwell]

@guiwrite a different error preventing the build on this one:

[ERROR] Client bundle compiled with errors therefore further build is impossible.
Error: MDX compilation failed for file "/vercel/path0/docs/docs/administration-and-security/billing-api-usage.md"
Cause: Image docs/administration-and-security/usage-graph.png used in docs/administration-and-security/billing-api-usage.md not found.
Details:
Error: Image docs/administration-and-security/usage-graph.png used in docs/administration-and-security/billing-api-usage.md not found.
    at async Promise.all (index 0)
Error: Command "npm run build" exited with 1

[robertnorrie]

Restructure looks fine. I think this one is ok to merge.