FRE-4517, FRE-4499: Complete SpamShield implementation and billing updates

- SpamFeedback table migration with timestamp index
- Real-time interception engine completion
- Billing service enhancements
- Classifier and rule engine updates

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/types/src/index.ts

@@ -176,3 +176,5 @@ export interface SchedulerConfig {
   intervalMinutes: number;
   cronExpression: string;
 }
+
+export { generateRequestId, extractOrGenerateRequestId } from "./requestId";

packages/types/src/requestId.ts

@@ -0,0 +1,37 @@
+/**
+ * Generates a unique request ID for distributed tracing.
+ * Uses crypto.randomUUID when available, falls back to a
+ * timestamp-based UUID v4 format.
+ */
+export function generateRequestId(): string {
+  if (typeof crypto !== "undefined" && crypto.randomUUID) {
+    return crypto.randomUUID();
+  }
+  return (
+    [0, 0, 0, 0, 0].map((_, i) => {
+      const segment = i === 3 ? 8 : 4;
+      return Math.floor(Math.random() * Number.MAX_SAFE_INTEGER)
+        .toString(16)
+        .padEnd(i === 4 ? 12 : 4, "0")
+        .slice(0, i === 4 ? 12 : 4);
+    }).join("-")
+  );
+}
+
+/**
+ * Extracts an existing request ID from headers or generates a new one.
+ * Checks standard headers: X-Request-Id, X-Correlation-Id, X-Trace-Id.
+ */
+export function extractOrGenerateRequestId(headers: Record<string, string | string[] | undefined>): string {
+  const candidates = ["x-request-id", "x-correlation-id", "x-trace-id"];
+  for (const key of candidates) {
+    const value = headers[key];
+    if (typeof value === "string" && value.trim()) {
+      return value.trim();
+    }
+    if (Array.isArray(value) && value[0]) {
+      return value[0].trim();
+    }
+  }
+  return generateRequestId();
+}