Pre-launch design sync with Figma spec (#2154)

* Add lookbook + viewcomponent, organize design system file

* Build menu component

* Button updates

* More button fixes

* Replace all menus with new ViewComponent

* Checkpoint: fix tests, all buttons and menus converted

* Split into Link and Button components for clarity

* Button cleanup

* Simplify custom confirmation configuration in views

* Finalize button, link component API

* Add toggle field to custom form builder + Component

* Basic tabs component

* Custom tabs, convert all menu / tab instances in app

* Gem updates

* Centralized icon helper

* Update all icon usage to central helper

* Lint fixes

* Centralize all disclosure instances

* Dialog replacements

* Consolidation of all dialog styles

* Test fixes

* Fix app layout issues, move to component with slots

* Layout simplification

* Flakey test fix

* Fix dashboard mobile issues

* Finalize homepage

* Lint fixes

* Fix shadows and borders in dark mode

* Fix tests

* Remove stale class

* Fix filled icon logic

* Move transparent? to public interface

app/views/layouts/shared/_nav_item.html.erb

@@ -0,0 +1,20 @@
+<%# locals:(name:, path:, icon:, icon_custom:, active:, mobile_only: false) %>
+
+<%= link_to path, class: "space-y-1 group block relative pb-1" do %>
+  <div class="grow flex flex-col lg:flex-row gap-1 items-center">
+    <%= tag.div class: class_names("w-4 h-1 lg:w-1 lg:h-4 rounded-bl-sm rounded-br-sm lg:rounded-tr-sm lg:rounded-br-sm lg:rounded-bl-none", "bg-nav-indicator" => active) %>
+
+    <%= tag.div class: class_names(
+      "w-8 h-8 flex items-center justify-center mx-auto rounded-lg",
+      active ? "bg-container shadow-xs text-primary" : "group-hover:bg-container-hover text-secondary"
+    ) do %>
+      <%= icon(icon, color: active ? "current" : "default", custom: icon_custom) %>
+    <% end %>
+  </div>
+
+  <div class="grow flex justify-center lg:pl-2">
+    <%= tag.p class: class_names("font-medium text-[11px]", active ? "text-primary" : "text-secondary") do %>
+      <%= name %>
+    <% end %>
+  </div>
+<% end %>