Add room info pane and room reporting flow

[tyreseluo]

Summary

This PR adds a new Room Info experience and room reporting flow in the room screen.

Changes

• Add RoomInfoSlidingPane with:
  • room summary (name, id, avatar)
  • topic preview with expand/collapse
  • room facts (visibility, encryption)
  • people page with member entries and incremental loading
• Add actions from room info pane:
  • open people profile
  • report room
  • leave room (with confirmation modal)
• Add ReportRoomModal with reason validation and submit/cancel actions
• Add MatrixRequest::ReportRoom and async handling in sliding_sync
• Add report result actions and success/error notifications
• Add room-info entry button in input bar (room_info_card_button) to open room info pane

Notes

• Threads pane and room info pane are mutually hidden when switching.
• Room info pane refreshes data while visible.

Testing

• Manual verification recommended:
  • open Room Info from input bar
  • switch to People page and open member profile
  • submit Report Room with/without reason
  • leave room from Room Info and confirm behavior