feat: per-type notification filter toggles with bottom sheet

[barrydeen]

Summary

• Replace single-select notification filter dropdown with a bottom sheet featuring per-type toggle switches and icons
• Each notification type (replies, reactions, zaps, reposts, mentions, votes, DMs) can be independently enabled/disabled — controlling both list visibility and sound/haptics
• Add separate "Chat rooms" toggle to hide all group chat notifications independently
• Top bar now shows a filter icon (tinted when filters active) and the existing sound toggle icon
• Filter state and chat rooms toggle persisted via SharedPreferences with migration from old single-filter pref

Test plan

• Open notifications screen, tap filter (tune) icon → bottom sheet appears with 7 type toggles + chat rooms toggle
• Toggle off a type → notifications of that type disappear from list
• Toggle off "Chat rooms" → group chat notifications hidden, regular notifications still visible
• Toggle off a type + receive that notification type → no sound/haptic
• Global sound toggle (volume icon) still mutes all sounds independently of type toggles
• "Enable all" / "Disable all" buttons work correctly
• Kill and restart app → all toggle states persist
• Verify migration: existing users with old filter pref get all types enabled on first launch