refactor(dav): improve readability of Sabre File::put upload flow

[joshtrichards]

• Resolves: #

Summary

This is a fairly mechanical refactor of OCA\DAV\Connector\Sabre\File::put() to improve readability and maintainability without intentionally changing behavior.

Why

put() is really long and handles several responsibilities at once:

• direct vs part-file uploads
• locking
• stream writing
• size validation
• rename/finalization
• metadata updates
• hook emission
• exception translation

This change keeps the existing flow but makes the method easier to follow by turning it into a higher-level orchestration method.

What changed

• extracted repeated exclusive-lock acquisition into a helper
• extracted request-body normalization into a helper
• extracted requested hash wrapping into a helper
• extracted content-length parsing and written-size validation into helpers
• extracted upload target resolution into resolveUploadTarget()
• extracted part-file finalization into a helper
• extracted upload metadata / checksum handling into a helper
• clarified local variable names in put()
• cleaned up and added comments to better explain control flow and intent

Notes

• no intentional behavior changes
• checksum handling is preserved as-is
• hook timing is preserved:
  • direct writes emit pre-hooks before writing the final target
  • part-file uploads emit pre-hooks before the final rename

Testing

• no new tests added
• intended as a readability/maintainability refactor only

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI