Line wrap toggle for editor and paste viewer with remembered preference (#130)

- wrap toggle button on /new editor and paste view (accent active state)
- flips white-space pre <-> pre-wrap on the code body
- shared localStorage preference palette-wrap, default off
- settings checkbox reads and writes the same preference

internal/web/static/app.css

@@ -691,3 +691,8 @@ button[type="submit"]:focus-visible,
 .attachment-chip:hover { border-color: var(--accent); }
 .attachment-chip .attachment-size { color: var(--muted-fg); font-size: 19px; }
 .attachment-preview img { max-width: 480px; max-height: 360px; border-radius: var(--radius); border: 1px solid var(--border); }
+
+/* line wrap toggle (#130): body wrap variants + toggle button */
+.editor.wrap, .codebody.wrap { white-space: pre-wrap; word-break: break-word; }
+.wrap-toggle[aria-pressed="true"] { background: var(--accent); color: var(--bg); border-color: var(--accent); }
+.editor-tools { display: flex; justify-content: flex-end; }