fix: gracefully handle localStorage quota exceeding

[Antreesy]

☑️ Resolves

• Fix Error while fetching conversations: QuotaExceededError #17602
  • wrap dangerous function call with try-catch
  • if it is an expected error, disable caching for conversations, no longer try to save in this session
  • impact is minimal, should affect only users with 1000+ rooms, but other

AI (if applicable)

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

🖌️ UI Checklist

To test: add a loop to cacheConversations to bloat the size of stored characters

		for (let i = 0; i < 5; i++) {
			conversations.push(...conversations)
		}

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
Broken UI

🚧 Tasks

• Follow-up: migrate to IndexedDB
  • Better chunking + caching on each change (now limited to deleting room + 30-sec update)

🏁 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

[Antreesy]

/backport to stable33

[Antreesy]

/backport to stable32