fix(security): add SSRF protection to vision_tools and web_tools (hardened)

* fix(security): add SSRF protection to vision_tools and web_tools

Both vision_analyze and web_extract/web_crawl accept arbitrary URLs
without checking if they target private/internal network addresses.
A prompt-injected or malicious skill could use this to access cloud
metadata endpoints (169.254.169.254), localhost services, or private
network hosts.

Adds a shared url_safety.is_safe_url() that resolves hostnames and
blocks private, loopback, link-local, and reserved IP ranges. Also
blocks known internal hostnames (metadata.google.internal).

Integrated at the URL validation layer in vision_tools and before
each website_policy check in web_tools (extract, crawl).

* test(vision): update localhost test to reflect SSRF protection

The existing test_valid_url_with_port asserted localhost URLs pass
validation. With SSRF protection, localhost is now correctly blocked.
Update the test to verify the block, and add a separate test for
valid URLs with ports using a public hostname.

* fix(security): harden SSRF protection — fail-closed, CGNAT, multicast, redirect guard

Follow-up hardening on top of dieutx's SSRF protection (PR #2630):

- Change fail-open to fail-closed: DNS errors and unexpected exceptions
  now block the request instead of allowing it (OWASP best practice)
- Block CGNAT range (100.64.0.0/10): Python's ipaddress.is_private
  does NOT cover this range (returns False for both is_private and
  is_global). Used by Tailscale/WireGuard and carrier infrastructure.
- Add is_multicast and is_unspecified checks: multicast (224.0.0.0/4)
  and unspecified (0.0.0.0) addresses were not caught by the original
  four-check chain
- Add redirect guard for vision_tools: httpx event hook re-validates
  each redirect target against SSRF checks, preventing the classic
  redirect-based SSRF bypass (302 to internal IP)
- Move SSRF filtering before backend dispatch in web_extract: now
  covers Parallel and Tavily backends, not just Firecrawl
- Extract _is_blocked_ip() helper for cleaner IP range checking
- Add 24 new tests (CGNAT, multicast, IPv4-mapped IPv6, fail-closed
  behavior, parametrized blocked/allowed IP lists)
- Fix existing tests to mock DNS resolution for test hostnames

---------

Co-authored-by: dieutx <dangtc94@gmail.com>

tests/tools/test_website_policy.py

@@ -343,6 +343,8 @@ def test_browser_navigate_allows_when_shared_file_missing(monkeypatch, tmp_path)
 async def test_web_extract_short_circuits_blocked_url(monkeypatch):
     from tools import web_tools
 
+    # Allow test URLs past SSRF check so website policy is what gets tested
+    monkeypatch.setattr(web_tools, "is_safe_url", lambda url: True)
     monkeypatch.setattr(
         web_tools,
         "check_website_access",
@@ -389,6 +391,9 @@ def test_check_website_access_fails_open_on_malformed_config(tmp_path, monkeypat
 async def test_web_extract_blocks_redirected_final_url(monkeypatch):
     from tools import web_tools
 
+    # Allow test URLs past SSRF check so website policy is what gets tested
+    monkeypatch.setattr(web_tools, "is_safe_url", lambda url: True)
+
     def fake_check(url):
         if url == "https://allowed.test":
             return None
@@ -428,6 +433,8 @@ async def test_web_crawl_short_circuits_blocked_url(monkeypatch):
 
     # web_crawl_tool checks for Firecrawl env before website policy
     monkeypatch.setenv("FIRECRAWL_API_KEY", "fake-key")
+    # Allow test URLs past SSRF check so website policy is what gets tested
+    monkeypatch.setattr(web_tools, "is_safe_url", lambda url: True)
     monkeypatch.setattr(
         web_tools,
         "check_website_access",
@@ -457,6 +464,8 @@ async def test_web_crawl_blocks_redirected_final_url(monkeypatch):
 
     # web_crawl_tool checks for Firecrawl env before website policy
     monkeypatch.setenv("FIRECRAWL_API_KEY", "fake-key")
+    # Allow test URLs past SSRF check so website policy is what gets tested
+    monkeypatch.setattr(web_tools, "is_safe_url", lambda url: True)
 
     def fake_check(url):
         if url == "https://allowed.test":