feat: presence fix, voice ringing fix, user private notes + doc updates

- usePresenceUpdater: replace stale closure with readStatus() called at
  invocation time so changing custom status in Profile Settings is never
  silently overwritten by subsequent activity events
- CallEmbedProvider: fix m.space.parent state-key lookup by switching
  getStateEvent → getStateEvents (plural); space channel voice rooms no
  longer trigger the incoming-call ring/animation
- Add useUserNotes hook (io.lotus.user_notes account data, reactive via
  useAccountDataCallback, 500-char limit, cross-device sync)
- UserRoomProfile: add UserPrivateNotes textarea with 800ms debounced
  auto-save, saving indicator, char counter when <100 chars remain;
  shown only when viewing another user's profile
- LOTUS_FEATURES.md: add Private Notes section, Status Revert fix note,
  animation improvements subsection, Seasonal Themes section
- LOTUS_BUGS.md: mark presence revert + voice ringing bugs as resolved
- README.md + landing/index.html: document all new June 2026 features

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -58,7 +58,8 @@ The Lotus Chat logo (`lotus_chat.png`) is a derivative work based on the origina
 - LotusGuild Terminal Design System (TDS) — a CRT terminal-inspired dark theme
 - TDS light mode variant for daytime use
 - 20+ static chat background patterns
-- 5 animated chat backgrounds: Digital Rain, Star Drift, Grid Pulse, Aurora Flow, Fireflies
+- 5 animated chat backgrounds: Digital Rain, Star Drift, Grid Pulse, Aurora Flow, Fireflies (with improved per-layer looping, phosphor-flicker rain, fluid aurora sweep, and organic firefly bioluminescence)
+- 11 seasonal & holiday theme overlays — Halloween, Christmas, New Year, Autumn, Valentine's Day, St. Patrick's Day, Earth Day, Lunar New Year, April Fools', Deep Space, and Retro Arcade; auto-selected by date with a manual override in Settings → Appearance
 - Toggle to pause background animations
 - Glassmorphism sidebar — frosted glass effect that lets the background show through
 - Night Light / blue light filter with an adjustable intensity slider
@@ -69,10 +70,11 @@ The Lotus Chat logo (`lotus_chat.png`) is a derivative work based on the origina
 ### Presence & Profile
 
 - Discord-style presence selector: Online, Idle, Do Not Disturb, Invisible, or Auto
-- Custom status message with emoji and an optional auto-clear timer
+- Custom status message with emoji and an optional auto-clear timer (changing your status is never silently overwritten by activity events)
 - Colored presence ring on member avatars (green / yellow / red)
 - Profile fields for pronouns and timezone
 - When a user's timezone is set, their current local time appears in their profile
+- Private notes on any user's profile — freeform text visible only to you, auto-saves and syncs across devices
 - Unread count shown in the browser tab title
 
 ### Moderation & Privacy