chore(deps): update python docker tag to v3.13.6

Author: renovate[bot]

Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: Install Python dependencies
-FROM python:3.13.5-slim@sha256:4c2cf9917bd1cbacc5e9b07320025bdb7cdf2df7b0ceaccb55e9dd7e30987419 AS python-builder
+FROM python:3.13.6-slim@sha256:2a928e11761872b12003515ea59b3c40bb5340e2e5ecc1108e043f92be7e473d AS python-builder
 
 WORKDIR /build
 
@@ -16,7 +16,7 @@ RUN set -eux; \
     pip install --no-cache-dir --timeout 1000 .[server,mcp]
 
 # Stage 2: Runtime image
-FROM python:3.13.5-slim@sha256:4c2cf9917bd1cbacc5e9b07320025bdb7cdf2df7b0ceaccb55e9dd7e30987419
+FROM python:3.13.6-slim@sha256:2a928e11761872b12003515ea59b3c40bb5340e2e5ecc1108e043f92be7e473d
 
 ARG UID=1000
 ARG GID=1000