Editor: font-size presets + image insert/export support

Two editor features that were in flight alongside the sound work:
- FontSize TipTap extension (rides on textStyle) with Small/Normal/Large/
  Title presets in the toolbar; StatusBar + CSS support
- Image handling: internal/images handler, upload route + config, client
  API, EditorCore wiring, and md/html/docx export support for images

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/components/StatusBar/SoundToggle.tsx

@@ -24,7 +24,7 @@ export function SoundToggle() {
       aria-pressed={on}
       title={on ? '声音开 · Sounds on' : '声音关 · Sounds off'}
       aria-label={on ? 'Mute Petal sounds' : 'Unmute Petal sounds'}
-      className="rounded-full px-1.5 py-0.5 transition-colors"
+      className="flex items-center justify-center rounded-full px-2 py-1 text-xl leading-none transition-colors"
       style={{ color: on ? 'var(--color-accent)' : 'var(--color-muted)', lineHeight: 1 }}
       onMouseEnter={(e) => (e.currentTarget.style.color = 'var(--color-accent-hover)')}
       onMouseLeave={(e) =>

web/src/components/StatusBar/StatusBar.tsx

@@ -45,7 +45,7 @@ export function StatusBar({ wordCount, text, saveStatus, checking, voicing, llmD
 
   return (
     <footer
-      className="flex h-9 shrink-0 items-center gap-3 px-6 text-xs"
+      className="flex h-11 shrink-0 items-center gap-3 px-6 text-sm"
       style={{ borderTop: '1px solid var(--color-border)', color: 'var(--color-muted)' }}
     >
       <div className="relative" ref={statsRef}>
@@ -54,7 +54,7 @@ export function StatusBar({ wordCount, text, saveStatus, checking, voicing, llmD
           onClick={() => setStatsOpen((o) => !o)}
           aria-haspopup="dialog"
           aria-expanded={statsOpen}
-          className="rounded-full px-1.5 py-0.5 font-semibold transition-colors"
+          className="rounded-full px-2 py-0.5 text-[0.95rem] font-bold transition-colors"
           style={{ color: statsOpen ? 'var(--color-accent-hover)' : 'inherit' }}
           onMouseEnter={(e) => (e.currentTarget.style.color = 'var(--color-accent-hover)')}
           onMouseLeave={(e) =>