chore: relax requires-python floor to >= 3.11

Lets the SDK install on Python 3.11 consumers (most notably
scaleapi/scaleapi's egp-api-backend, which is pinned to 3.11 alongside
7 other monorepo packages). Verified the SDK source parses cleanly at
ast.parse(feature_version=(3, 11)) over every .py file — no PEP 695
type params, no type statement, no other 3.12-only syntax.

Declan approved the relax in conversation with Max Parke.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: max-parke-scale

pyproject.toml

@@ -56,10 +56,11 @@ dependencies = [
     "opentelemetry-api>=1.20.0",
 ]
 
-requires-python = ">= 3.12,<4"
+requires-python = ">= 3.11,<4"
 classifiers = [
   "Typing :: Typed",
   "Intended Audience :: Developers",
+  "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: 3.13",
   "Programming Language :: Python :: 3.14",