feat: 5 dramatic extra themes (neon/terminal/blueprint/sunset) + board/review/layout polish

- Themes: add neon (cyber gradient), terminal (green CRT), blueprint (graph
  paper) and sunset (vaporwave) alongside the default Light (Y2K paper) and
  Dark. Theme toggle now cycles all; profile selector lists them; server
  validates against a shared whitelist.
- Bounty cards now show the project (customer) name.
- Remove the celebratory emoji from the empty Review Queue.
- Full-width h1 underline rule; My Tasks columns stack vertically for more
  room per task; card action buttons wrap/right-align so they never overflow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/http/profile_integration_test.go

@@ -108,7 +108,7 @@ func TestProfilePatchAndThemePersistence(t *testing.T) {
 
 	// invalid theme rejected
 	resp = patchJSON(t, c, ts.URL+"/api/v1/profile", map[string]any{
-		"settings": map[string]any{"theme": "neon"},
+		"settings": map[string]any{"theme": "rainbow-unicorn"},
 	}, csrf)
 	if resp.StatusCode != http.StatusBadRequest {
 		t.Fatalf("invalid theme: %d", resp.StatusCode)