docs(admin): improve nginx config php location block structure and clarity

[joshtrichards]

☑️ Resolves

Improve the comments and formatting of the PHP block (location ~ \.php(?:$|/) {...}) in both nginx sample configuration files to make them clearer and more maintainable. Re-ordered the regex in the rewrite merely for logical clarity, but no functional changes.

Changes:

• Rewrite the PHP location block comments to clearly document the front-controller rewrite regex, its exceptions, and why ordering matters
• Reorder rewrite regex ordering to be slightly more logically grouped and, in turn, make easier to document/follow (core entry points / OCS endpoints / update/updater endpoints / app exceptions)
• Add explanatory comments to previously uncommented directives
• Add a file header identifying each sample as root vs. subdirectory installation
• Add upstream block heading comment clarifying "use one, not both"
• Fix mixed tab/space indentation in the types block
• Align both sample files to use a consistent comment style

🖼️ Screenshots

root installation:

subdirectory installation: