Unify the dashboard experience and retire the multi-theme engine so onboarding and day-to-day invoicing feel consistent and easier to maintain.

Shared layout, tabs, and sidebar timer; user onboarding and registration polish; settings danger zone and data export; chart and tRPC perf fixes; migrations for onboarding and dropped appearance columns.

Co-authored-by: Cursor <cursoragent@cursor.com>

drizzle/0018_user_onboarding.sql

@@ -0,0 +1,11 @@
+ALTER TABLE "beenvoice_user" ADD COLUMN IF NOT EXISTS "onboardingCompletedAt" timestamp;
+
+-- Users who already have a business are treated as onboarded
+UPDATE "beenvoice_user" u
+SET "onboardingCompletedAt" = COALESCE(u."onboardingCompletedAt", NOW())
+WHERE u."onboardingCompletedAt" IS NULL
+  AND EXISTS (
+    SELECT 1
+    FROM "beenvoice_business" b
+    WHERE b."createdById" = u."id"
+  );