Refactor to generic ERP base

Remove influencer-specific features (campaigns, TikTok, gifts, shadow ledger,
contracts, briefings) and consolidate into a clean ERP foundation with core
bookkeeping, invoicing, receipts, tax reporting, and calendar functionality.
Reorganize database migrations into a clean numbered sequence.

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

components/ui/empty-state.tsx

@@ -9,8 +9,6 @@ import {
   Users,
   ArrowLeftRight,
   Camera,
-  Gift,
-  Megaphone,
   Building2,
   FileText,
   Calendar,
@@ -143,32 +141,6 @@ export function EmptyReceipts() {
   )
 }
 
-export function EmptyGifts() {
-  return (
-    <EmptyState
-      icon={Gift}
-      title="Inga gåvor registrerade"
-      description="Fått produkter från varumärken? Registrera dem här för korrekt skattehantering."
-      actionLabel="Registrera gåva"
-      actionHref="/gifts/new"
-    />
-  )
-}
-
-export function EmptyCampaigns() {
-  return (
-    <EmptyState
-      icon={Megaphone}
-      title="Inga samarbeten"
-      description="Skapa samarbeten för att hålla koll på innehåll, deadlines och fakturering."
-      actionLabel="Skapa samarbete"
-      actionHref="/campaigns/new"
-      secondaryActionLabel="Importera avtal"
-      secondaryActionHref="/campaigns/import"
-    />
-  )
-}
-
 export function EmptyDeadlines() {
   return (
     <EmptyState