security: SSRF guard covers IPv6 + DNS-rebind defence via pinned IP (#49)

Expand the SSRF blocklist from IPv4-only to IPv6 loopback/ULA (fc00::/7)/
link-local (fe80::/10)/multicast/IPv4-mapped, plus the missing IPv4 ranges
0.0.0.0/8, 100.64.0.0/10 CGNAT, and TEST-NET/benchmark ranges. Replace the
single-lookup SSRF guard with resolveAndValidate(): resolves all DNS records
(lookup { all: true }) so a hostname returning "public + private" is
rejected, and returns the first validated address for connection pinning.

The webhook dispatcher now switches from plain fetch() to https.request()
with a custom Agent.lookup that returns the pre-validated IP. A DNS rebind
between the guard check and the TCP connect() can no longer redirect the
dial to an internal address. Hostname still flows through for SNI and
certificate validation.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/api/src/__tests__/user-router.test.ts

@@ -716,19 +716,26 @@ describe("user profile and TOTP self-service", () => {
       totpEnabled: false,
     });
     const update = vi.fn().mockResolvedValue({});
+    const updateMany = vi.fn().mockResolvedValue({ count: 1 });
     const caller = createAdminCaller({
       user: {
         findUnique,
         update,
+        updateMany,
       },
     });
 
     const result = await caller.verifyAndEnableTotp({ token: "123456" });
 
     expect(result).toEqual({ enabled: true });
+    // lastTotpAt is written atomically by updateMany (the replay guard);
+    // user.update only toggles the enabled flag after the CAS succeeds.
+    expect(updateMany).toHaveBeenCalledWith(
+      expect.objectContaining({ data: { lastTotpAt: expect.any(Date) } }),
+    );
     expect(update).toHaveBeenCalledWith({
       where: { id: "user_admin" },
-      data: { totpEnabled: true, lastTotpAt: expect.any(Date) },
+      data: { totpEnabled: true },
     });
   });
 
@@ -743,10 +750,12 @@ describe("user profile and TOTP self-service", () => {
       lastTotpAt: null,
     });
     const update = vi.fn().mockResolvedValue({});
+    const updateMany = vi.fn().mockResolvedValue({ count: 1 });
     const caller = createAdminCaller({
       user: {
         findUnique,
         update,
+        updateMany,
       },
     });
 
@@ -757,10 +766,9 @@ describe("user profile and TOTP self-service", () => {
       where: { id: "user_admin" },
       select: { id: true, totpSecret: true, totpEnabled: true, lastTotpAt: true },
     });
-    expect(update).toHaveBeenCalledWith({
-      where: { id: "user_admin" },
-      data: { lastTotpAt: expect.any(Date) },
-    });
+    expect(updateMany).toHaveBeenCalledWith(
+      expect.objectContaining({ data: { lastTotpAt: expect.any(Date) } }),
+    );
   });
 
   it("rejects invalid login-flow TOTP tokens with UNAUTHORIZED", async () => {