feat(registratura): atomic numbering, reserved slots, audit trail, API endpoints + theme toggle animation

Registratura module:
- Atomic sequence numbering (BTG-2026-IN-00125 format) via PostgreSQL upsert
- Reserved monthly slots (2/company/month) for late registrations
- Append-only audit trail with diff tracking
- REST API: /api/registratura (CRUD), /api/registratura/reserved, /api/registratura/audit
- Auth: NextAuth session + Bearer API key support
- New "intern" direction type with UI support (form, filters, table, detail panel)
- Prisma models: RegistrySequence, RegistryAudit

Theme toggle:
- SVG mask-based sun/moon morph with 360° spin animation
- Inverted logic (sun in dark mode, moon in light mode)

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

prisma/schema.prisma

@@ -82,3 +82,33 @@ model GisUat {
   @@index([name])
   @@index([county])
 }
+
+// ─── Registratura: Atomic Sequences + Audit ────────────────────────
+
+model RegistrySequence {
+  id        String   @id @default(uuid())
+  company   String   // BTG, SDT, USW, GRP
+  year      Int
+  type      String   // IN, OUT, INT
+  lastSeq   Int      @default(0)
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  @@unique([company, year, type])
+  @@index([company, year])
+}
+
+model RegistryAudit {
+  id          String   @id @default(uuid())
+  entryId     String
+  entryNumber String
+  action      String   // created, updated, reserved_created, reserved_claimed, late_registration, closed, deleted
+  actor       String
+  actorName   String?
+  company     String
+  detail      Json?
+  createdAt   DateTime @default(now())
+
+  @@index([entryId])
+  @@index([company, createdAt])
+}