Bump python from 3.9-slim to 3.14-slim in /docker

Bumps python from 3.9-slim to 3.14-slim.

---
updated-dependencies:
- dependency-name: python
  dependency-version: 3.14-slim
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

docker/Dockerfile

@@ -2,7 +2,7 @@
 # Multi-stage build for smaller image size
 
 # Build stage
-FROM python:3.9-slim AS builder
+FROM python:3.14-slim AS builder
 
 WORKDIR /app
 
@@ -20,7 +20,7 @@ RUN pip install --no-cache-dir --upgrade pip && \
     pip install --no-cache-dir .
 
 # Runtime stage
-FROM python:3.9-slim AS runtime
+FROM python:3.14-slim AS runtime
 
 WORKDIR /app