feat(chat): message-list rework, customization surface, smooth scroll

Chat tab overhaul:
- Header/layout: single-row header (name + key-lock + compact click-to-copy address +
  right-aligned icon toolbar with a settings "notch"), composer moved below the message
  box (emoji toggle left of a bottom-flush input), tightened list-pane controls.
- Message list: per-day date separators (Today/Yesterday/date), time-only group headers,
  tight same-sender grouping with iMessage-style merged corners, per-run peer avatar,
  delivery status (clock -> check), hover-reveal per-message time. Message base ~18px.
- Customization: a settings "notch" gear opens a modal (also under Settings ->
  Chat & Contacts) with segmented controls for emoji style / bubble style / density /
  timestamps, sliders for poll rate + text size, a bubble-accent dropdown, Enter-to-send.
  Bubble style/accent/density/text-size/timestamps all applied live in the message loop.
- Settings: app-wide clock-format control lives in Settings -> General; chat keeps a
  per-tab override. Both chat panes now use the app's smooth wheel-scroll.
- i18n: new strings across all 8 languages; CJK subset rebuilt for the added glyphs.

Inline contact rename, hide/mute, 0-conf fast-scan and the export path are carried through.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/chat_tab.h

@@ -24,6 +24,18 @@ namespace ui {
  */
 void RenderChatTab(App* app);
 
+/**
+ * @brief Render the chat-customization controls (emoji style, poll rate, bubble style/color,
+ *        density, text size, chat timestamps, Enter-to-send). Shared by the Chat tab's settings
+ *        "notch" modal and the Settings tab's Chat & Contacts section. The app-wide clock format
+ *        (which chat timestamps fall back to) lives separately in Settings → General.
+ * @param app Pointer to the app instance.
+ * @param contentWidth Explicit row width for right-aligning controls; pass the card's inner content
+ *        width from the Settings tab (whose GlassCard doesn't narrow the content region). 0 = auto
+ *        (use the current content region, correct inside the chat modal's dialog).
+ */
+void RenderChatSettingsControls(App* app, float contentWidth = 0.0f);
+
 /**
  * @brief Securely wipe the Chat tab's UI-local state (composer / new-conversation
  *        plaintext buffers + the selected-conversation ids). Called by