feat(ui): add breadcrumb icons, fix alignment, and remove duplicate form headers

- add section icons to all breadcrumbs across every page
- fix breadcrumb nav display:flex so icons align vertically with buttons
- wrap all page breadcrumbs in pageToolbar div for consistent layout
- add Breadcrumbs to AllRunsPage which previously used a plain h1
- fix envCardHeader flex:1 so settings button hugs the right edge
- remove card header from environment create/edit forms (duplicated breadcrumb)

client/src/ui/Button/Button.module.css

@@ -11,6 +11,7 @@
   white-space: nowrap;
   outline: none;
   text-decoration: none;
+  box-shadow: var(--shadow-xs);
   transition:
     background var(--transition),
     border-color var(--transition),