feat(enterprise): add audit log archival with crash-safe state machine

tests/unit/api/audit-archival.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from "vitest";
+
+describe("audit archival state machine", () => {
+  const validTransitions: Record<string, string> = {
+    PENDING: "EXPORTING",
+    EXPORTING: "EXPORTED",
+    EXPORTED: "PURGING",
+    PURGING: "COMPLETE",
+  };
+
+  it("state transitions are valid", () => {
+    for (const [from, to] of Object.entries(validTransitions)) {
+      expect(from).toBeTruthy();
+      expect(to).toBeDefined();
+    }
+  });
+
+  it("covers all non-terminal states", () => {
+    const states = ["PENDING", "EXPORTING", "EXPORTED", "PURGING", "COMPLETE"];
+    const nonTerminal = states.filter((s) => s !== "COMPLETE");
+    for (const state of nonTerminal) {
+      expect(validTransitions[state]).toBeDefined();
+    }
+  });
+
+  it("COMPLETE is terminal (no outgoing transition)", () => {
+    expect(validTransitions.COMPLETE).toBeUndefined();
+  });
+
+  it("has no cycles in the transition graph", () => {
+    const visited = new Set<string>();
+    let current = "PENDING";
+    while (current && !visited.has(current)) {
+      visited.add(current);
+      current = validTransitions[current];
+    }
+    // If we exited because current is undefined (end of chain), no cycle
+    expect(current).toBeUndefined();
+  });
+});