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/Editor/FontSize.ts

@@ -0,0 +1,51 @@
+import { Extension } from '@tiptap/core'
+
+// FontSize adds a `fontSize` attribute to the textStyle mark so a writer can
+// pick a size preset (Small / Normal / Large / Title) from the toolbar. It rides
+// on TextStyle (already loaded) rather than introducing a new mark, so it stacks
+// cleanly with color and other inline styling.
+declare module '@tiptap/core' {
+  interface Commands<ReturnType> {
+    fontSize: {
+      setFontSize: (size: string) => ReturnType
+      unsetFontSize: () => ReturnType
+    }
+  }
+}
+
+export const FontSize = Extension.create({
+  name: 'fontSize',
+
+  addOptions() {
+    return { types: ['textStyle'] }
+  },
+
+  addGlobalAttributes() {
+    return [
+      {
+        types: this.options.types,
+        attributes: {
+          fontSize: {
+            default: null,
+            parseHTML: (element) => element.style.fontSize || null,
+            renderHTML: (attributes) =>
+              attributes.fontSize ? { style: `font-size: ${attributes.fontSize}` } : {},
+          },
+        },
+      },
+    ]
+  },
+
+  addCommands() {
+    return {
+      setFontSize:
+        (size) =>
+        ({ chain }) =>
+          chain().setMark('textStyle', { fontSize: size }).run(),
+      unsetFontSize:
+        () =>
+        ({ chain }) =>
+          chain().setMark('textStyle', { fontSize: null }).removeEmptyTextStyle().run(),
+    }
+  },
+})