Import/Export UX improvements (#16619)

Import/Export UX improvements (#16619)

* webui : added download action (#13552)

* webui : import and export (for all conversations)

* webui : fixed download-format, import of one conversation

* webui : add ExportedConversations type for chat import/export

* feat: Update naming & order

* chore: Linting

* feat: Import/Export UX improvements

* chore: update webui build output

* feat: Update UI placement of Import/Export tab in Chat Settings Dialog

* refactor: Cleanup

chore: update webui build output

* feat: Enable shift-click multiple conversation items selection

* chore: update webui static build

* chore: update webui static build

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Co-authored-by: Sascha Rogmann <redacted>