feat(conversationfolder): add frontend support for per-share conversa…

[miaulalala]

…tion subfolders

Adds the API call layer and upload store integration to use the new POST /api/v1/chat/{token}/attachment endpoint when conversation subfolders are enabled.

AI-assisted-by: Claude Sonnet 4.6 noreply@anthropic.com

☑️ Resolves

• Fix 📂 Use subfolder for Talk attachments, one per conversation #4340
• Ref feat(conversationfolder): use per share conversation folders #17346

AI (if applicable)

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

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
Screenshot before	Screenshot after

🚧 Tasks

• ...

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

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🛠️ API Checklist

🚧 Tasks

• ...

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed

[Antreesy]

Some backend questions:

1. HPB failing to get the file, maybe because it's in draft fodler?

2. Incoming shared folders (Bob > Alice) do not appear in file treed, as it's shared from files/Talk/Alice-token/Bob-bob to files/Talk/Bob-token/Bob-bob. What's the state on sharing support for 1-1 conversations?
   Asking because this bit is ignored for default share - and if Talk/ folder is missing, it will fail:

bb1a36d#diff-42169075c6c4b6aaa56b2023cc035b0e088ac7f76fd7d94ebd4b9e3af0d50a4eR60-R67

cc @miaulalala

[Antreesy]

Adjusted lint, tests, and rename logic to work correctly. removed conditions for public/group, works with all conversations, as it's supposed to
Please rebase onto main, test once more and then squash fixups. Works nice! 🧑‍🍳🤌