ui: drop remaining T212-only framing from dashboard + import lede

- portfolio.js empty-state CTA: "Import a T212 CSV" → "Import a portfolio CSV"
- settings.html lede: lead with broker-agnostic copy; relegate the T212
  export path to a smaller secondary line.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/js/portfolio.js

@@ -189,7 +189,7 @@
       '<div class="empty" style="padding:16px;">' +
         notice +
         'No portfolio loaded in this browser. ' +
-        '<a href="/settings#import">Import a T212 CSV →</a>' +
+        '<a href="/settings#import">Import a portfolio CSV →</a>' +
       '</div>';
   }