security: Fix all Dependabot vulnerabilities

- Upgrade urllib3 to >=2.6.0 (fixes CVE for streaming/decompression)
- Pin h11>=0.16.0 (fixes critical chunked encoding vulnerability)
- Update requires-python to >=3.9 (urllib3 2.6+ requirement)
- Add Python 3.13 classifier, remove 3.8

Addresses all 7 Dependabot alerts:
- h11 critical: malformed Chunked-Encoding bodies
- urllib3 high: streaming API compression issues (2x)
- urllib3 medium: redirect handling (2x)
- requests medium: .netrc credentials leak
- aiohttp low: HTTP smuggling

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "hanzoai"
-version = "2.1.1"
+version = "2.1.2"
 description = "The official Python library for the Hanzo API"
 dynamic = ["readme"]
 license = "BSD-3-Clause"
@@ -14,16 +14,19 @@ dependencies = [
     "anyio>=3.5.0, <5",
     "distro>=1.7.0, <2",
     "sniffio",
+    # Security: pin minimum versions to address vulnerabilities
+    "h11>=0.16.0",
+    "urllib3>=2.6.0",
 ]
-requires-python = ">= 3.8"
+requires-python = ">= 3.9"
 classifiers = [
   "Typing :: Typed",
   "Intended Audience :: Developers",
-  "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
   "Operating System :: OS Independent",
   "Operating System :: POSIX",
   "Operating System :: MacOS",