fix: resolve DNS before SSRF check and block redirects in parse-url

isPrivateUrl() did string-only hostname matching and never resolved DNS,
so a public-looking name that maps to an internal IP (e.g.
127-0-0-1.sslip.io -> 127.0.0.1) passed the check while fetch/extract
later resolved it and reached internal services (GHSA-wqcv-5qvx-vx75).

- isPrivateUrl is now async: it keeps the fast string/literal-IP path,
  then resolves the hostname via DNS and rejects if any address is private.
- parse-url now fetches the page itself with redirect: "error" and parses
  via extractFromHtml(), since article-extractor follows redirects
  internally and drops a redirect option, which allowed a public URL to
  302 to an internal host.
- Update validate-model call site to await; add regression tests.

tests/unit/ssrf-protection.test.ts

@@ -1,21 +1,62 @@
-import { describe, expect, it } from "vitest"
+import { beforeEach, describe, expect, it, vi } from "vitest"
 import { isPrivateUrl } from "@/lib/ssrf-protection"
 
+// Mock DNS so tests are deterministic and never hit the network.
+const lookupMock = vi.hoisted(() => vi.fn())
+vi.mock("node:dns/promises", () => ({
+    default: { lookup: lookupMock },
+    lookup: lookupMock,
+}))
+
 describe("isPrivateUrl", () => {
-    it("blocks private IPv6 URLs", () => {
-        expect(isPrivateUrl("http://[::1]/")).toBe(true)
-        expect(isPrivateUrl("http://[0:0:0:0:0:0:0:1]/")).toBe(true)
-        expect(isPrivateUrl("http://[::]/")).toBe(true)
-        expect(isPrivateUrl("http://[::ffff:127.0.0.1]/")).toBe(true)
-        expect(isPrivateUrl("http://[fc00::1]/")).toBe(true)
-        expect(isPrivateUrl("http://[fd12:3456:789a::1]/")).toBe(true)
-        expect(isPrivateUrl("http://[fe80::1]/")).toBe(true)
-        expect(isPrivateUrl("http://[fe9f::1]/")).toBe(true)
-        expect(isPrivateUrl("http://[febf::1]/")).toBe(true)
+    beforeEach(() => {
+        lookupMock.mockReset()
     })
 
-    it("allows public URLs", () => {
-        expect(isPrivateUrl("https://example.com/article")).toBe(false)
-        expect(isPrivateUrl("https://fc00.example.com/article")).toBe(false)
+    it("blocks private IPv6 URLs (string-only fast path, no DNS)", async () => {
+        expect(await isPrivateUrl("http://[::1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[0:0:0:0:0:0:0:1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[::]/")).toBe(true)
+        expect(await isPrivateUrl("http://[::ffff:127.0.0.1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[fc00::1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[fd12:3456:789a::1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[fe80::1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[fe9f::1]/")).toBe(true)
+        expect(await isPrivateUrl("http://[febf::1]/")).toBe(true)
+        expect(lookupMock).not.toHaveBeenCalled()
+    })
+
+    it("blocks literal private IPv4 without DNS", async () => {
+        expect(await isPrivateUrl("http://127.0.0.1/")).toBe(true)
+        expect(await isPrivateUrl("http://10.0.0.5/")).toBe(true)
+        expect(await isPrivateUrl("http://192.168.1.1/")).toBe(true)
+        expect(await isPrivateUrl("http://169.254.169.254/")).toBe(true)
+        expect(lookupMock).not.toHaveBeenCalled()
+    })
+
+    it("allows public URLs that resolve to public IPs", async () => {
+        lookupMock.mockResolvedValue([{ address: "93.184.216.34", family: 4 }])
+        expect(await isPrivateUrl("https://example.com/article")).toBe(false)
+    })
+
+    it("blocks public-looking hostnames that resolve to a private IP (DNS-rebinding-style bypass)", async () => {
+        // e.g. 127-0-0-1.sslip.io resolves to 127.0.0.1
+        lookupMock.mockResolvedValue([{ address: "127.0.0.1", family: 4 }])
+        expect(await isPrivateUrl("http://127-0-0-1.sslip.io/")).toBe(true)
+    })
+
+    it("blocks when any resolved address is private", async () => {
+        lookupMock.mockResolvedValue([
+            { address: "93.184.216.34", family: 4 },
+            { address: "10.1.2.3", family: 4 },
+        ])
+        expect(await isPrivateUrl("http://mixed.example.com/")).toBe(true)
+    })
+
+    it("blocks when DNS resolution fails", async () => {
+        lookupMock.mockRejectedValue(new Error("ENOTFOUND"))
+        expect(await isPrivateUrl("http://does-not-resolve.example/")).toBe(
+            true,
+        )
     })
 })