docs: sync Chatroom_Feature_Review.md with v1.8.0 changes

Bump document to v1.8.0 and update sections to reflect implemented
changes:

- §7: Remove ChannelContext, add useSheetStore hardening notes
- §9: Add useBottomSheet hook entry
- §11: Add v1.8.0 mobile hardening table (10 fixes)
- §22: Mark design system violations as fixed
- §23: Add useBottomSheet.ts, mark ChannelProvider.tsx as deleted
- §24: Resolve T7 (ChannelProvider) and T14 (mobile ChannelProvider)
- §25: Check off completed roadmap items across phases 1–6
- §31: Mark ChannelProvider compound audit problem as resolved
- §32: Update DS compliance scores and icon migration ratio

Author: HMarzban