Add line wrap toggle for editor and paste viewer (#130)

Shared client-side preference in localStorage 'palette-wrap', default
off. Toggle button on /new editor head and paste title bar, plus a Line
wrap checkbox in the settings menu; all read/write the same preference.
Active state uses the accent treatment like other toggles. No em dashes
in UI text.

internal/web/static/app.css

@@ -237,6 +237,11 @@ body {
 .theme-card .swatch { width: 26px; height: 26px; border-radius: 6px; border: 1px solid rgba(255,255,255,.15); }
 .theme-name { font-weight: 600; }
 .iconbtn:hover { color: var(--fg); border-color: var(--muted); }
+/* #130: line wrap toggle, accent when active like other toggles */
+.iconbtn.wrap-toggle[aria-pressed="true"],
+.btn-icon.wrap-toggle[aria-pressed="true"] { background: var(--accent); color: var(--bg); border-color: var(--accent); }
+html[data-wrap] .codebody { white-space: pre-wrap; }
+html[data-wrap] .editor { white-space: pre-wrap; }
 .iconbtn.danger:hover { color: #ff8fa3; border-color: #ff8fa3; }
 .code-head {
   display: flex; align-items: center; gap: 10px; padding: 8px 16px;