Add privacy mode with blur toggle for financial data

- Stimulus controller on global layout (persists across all pages)
- CSS blur effect on .privacy-sensitive elements (8px active, 4px on hover)
- localStorage persistence survives page navigations
- Toggle button on dashboard with aria-pressed for accessibility
- Applied to 28+ views: accounts, budgets, transactions, reports, etc.

Fixes: UTF-8 encoding, global controller mount, aria-pressed attribute

app/views/shared/_trend_change.html.erb

@@ -1,6 +1,6 @@
 <%# locals: { trend:, comparison_label: nil } %>
 
-<p class="text-sm" style="color: <%= trend.color %>">
+<p class="text-sm privacy-sensitive" style="color: <%= trend.color %>">
   <% if trend.direction.flat? %>
     <%= t(".no_change") %><%= " #{comparison_label}" if defined?(comparison_label) && comparison_label.present? %>
   <% else %>