Onboarding: use ocean background image, show full expertise tag names

- Replace blue gradient with ocean.png background (matches email templates)
- Display expertise tags one per line with full names (no truncation)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/shared/expertise-select.tsx

@@ -212,7 +212,7 @@ export function ExpertiseSelect({
                 </button>
 
                 {isExpanded && (
-                  <div className="grid grid-cols-1 sm:grid-cols-2 gap-1 p-2">
+                  <div className="grid grid-cols-1 gap-1 p-2">
                     {categoryTags.map((tag) => {
                       const isSelected = value.includes(tag.name)
                       const isLocked = isTagLocked(tag.name)
@@ -261,7 +261,7 @@ export function ExpertiseSelect({
                                 <Check className="h-2 w-2 text-white" />
                               ))}
                           </div>
-                          <span className="text-xs truncate">{tag.name}</span>
+                          <span className="text-xs">{tag.name}</span>
                         </Button>
                       )
                     })}