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>

src/modules/registratura/services/audit-service.ts

@@ -0,0 +1,126 @@
+/**
+ * Append-only audit trail for Registratura entries.
+ * Server-side only — uses Prisma directly.
+ */
+
+import { prisma } from "@/core/storage/prisma";
+import { Prisma } from "@prisma/client";
+import type { RegistryAuditAction, RegistryAuditEvent } from "../types";
+
+/** Log a single audit event (append-only, never updated or deleted) */
+export async function logAuditEvent(params: {
+  entryId: string;
+  entryNumber: string;
+  action: RegistryAuditAction;
+  actor: string;
+  actorName?: string;
+  company: string;
+  detail?: Record<string, unknown>;
+}): Promise<void> {
+  await prisma.registryAudit.create({
+    data: {
+      entryId: params.entryId,
+      entryNumber: params.entryNumber,
+      action: params.action,
+      actor: params.actor,
+      actorName: params.actorName ?? null,
+      company: params.company,
+      detail: (params.detail as Prisma.InputJsonValue) ?? Prisma.JsonNull,
+    },
+  });
+}
+
+/** Get chronological audit history for a single entry */
+export async function getAuditHistory(
+  entryId: string,
+): Promise<RegistryAuditEvent[]> {
+  const rows = await prisma.registryAudit.findMany({
+    where: { entryId },
+    orderBy: { createdAt: "asc" },
+  });
+  return rows.map(mapRow);
+}
+
+/** Get audit events for a company, optionally filtered by date range */
+export async function getAuditByCompany(
+  company: string,
+  options?: { from?: string; to?: string; limit?: number },
+): Promise<RegistryAuditEvent[]> {
+  const where: Prisma.RegistryAuditWhereInput = { company };
+
+  if (options?.from || options?.to) {
+    const createdAt: Prisma.DateTimeFilter = {};
+    if (options.from) createdAt.gte = new Date(options.from);
+    if (options.to) createdAt.lte = new Date(options.to);
+    where.createdAt = createdAt;
+  }
+
+  const rows = await prisma.registryAudit.findMany({
+    where,
+    orderBy: { createdAt: "desc" },
+    take: options?.limit ?? 100,
+  });
+  return rows.map(mapRow);
+}
+
+/** Compute diff between old and new entry for "updated" audit events */
+export function computeEntryDiff(
+  oldEntry: Record<string, unknown>,
+  newEntry: Record<string, unknown>,
+  fieldsToTrack: string[],
+): Record<string, { old: unknown; new: unknown }> | null {
+  const changes: Record<string, { old: unknown; new: unknown }> = {};
+
+  for (const field of fieldsToTrack) {
+    const oldVal = oldEntry[field];
+    const newVal = newEntry[field];
+    if (JSON.stringify(oldVal) !== JSON.stringify(newVal)) {
+      changes[field] = { old: oldVal, new: newVal };
+    }
+  }
+
+  return Object.keys(changes).length > 0 ? changes : null;
+}
+
+// ── Internal helpers ──
+
+function mapRow(r: {
+  id: string;
+  entryId: string;
+  entryNumber: string;
+  action: string;
+  actor: string;
+  actorName: string | null;
+  company: string;
+  detail: Prisma.JsonValue;
+  createdAt: Date;
+}): RegistryAuditEvent {
+  return {
+    id: r.id,
+    entryId: r.entryId,
+    entryNumber: r.entryNumber,
+    action: r.action as RegistryAuditAction,
+    actor: r.actor,
+    actorName: r.actorName ?? undefined,
+    company: r.company,
+    detail: (r.detail as Record<string, unknown>) ?? undefined,
+    createdAt: r.createdAt.toISOString(),
+  };
+}
+
+/** Fields tracked for update diffs */
+export const TRACKED_FIELDS = [
+  "subject",
+  "sender",
+  "recipient",
+  "direction",
+  "documentType",
+  "status",
+  "company",
+  "deadline",
+  "assignee",
+  "date",
+  "notes",
+  "tags",
+  "expiryDate",
+];