docs(dev/WebDAV): expand and correct basic operations reference

[joshtrichards]

☑️ Resolves

Overhauls the WebDAV basic operations page in the developer manual.

New content:

• Quick method/header cheat sheet table
• Missing properties: nc:is-federated, nc:metadata_etag, nc:download-url-expiration, dynamic nc:metadata-*
• X-Requested-With requirement for non-GET requests on public share endpoints
• X-Hash: all option, OC-Checksum bulk upload validation behavior, X-NC-WebDAV-AutoMkcol availability note (NC 32+)
• Shorthand zip/tar values for folder download accept parameter

Clarifications:

• Renamed page: "Basic APIs" to "Basic File & Folder Operations"
• Expanded intro with file path pattern and 2FA app-password guidance
• Noted oc:permissions S/M flag stripping on public shares
• Added URL-encoding reminder for query-parameter folder downloads
• Added note distinguishing standard WebDAV vs Nextcloud-specific property namespaces

Changes:

• Typos: "head" > "header", oc-favorite > oc:favorite, missing periods
• Broken XML: corrected ocm namespace url syntax, fixed indentation and missing </d:propfind> closing tag
• Self-closing tag syntax: nc:is-mount-root, nc:hidden
• Improved the Supported properties table layout: column widths

🖼️ Screenshots