feat(config): add pageWidth setting to .remanso.json

Allows repo owners to configure note column width via `"pageWidth": "700px"` in .remanso.json. Applies the value to the --note-width CSS variable and invalidates the cached width so resize/overlay hooks pick it up.

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

src/modules/repo/interfaces/UserSettings.ts

@@ -10,4 +10,5 @@ export interface UserSettings extends Model<DataType.UserSettings> {
   backlink?: boolean
   chosenTitleFont?: string
   chosenBodyFont?: string
+  pageWidth?: string
 }

src/modules/user/hooks/useUserSettings.hook.ts

@@ -1,5 +1,6 @@
 import { watchEffect } from "vue"
 
+import { resetNoteWidthCache } from "@/constants/note-width"
 import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
 import { downloadFont } from "@/utils/downloadFont"
 
@@ -22,5 +23,11 @@ export const useUserSettings = () => {
       "--title-font-family"
     )
     root.style.setProperty("--font-size", fontSize || DEFAULT_FONT_SIZE)
+
+    const pageWidth = store.userSettings?.pageWidth
+    if (pageWidth) {
+      root.style.setProperty("--note-width", pageWidth)
+      resetNoteWidthCache()
+    }
   })
 }