fix(core): escape backslash in sed command for CRLF stripping in Dockerfile template

The sed pattern 's/\r$//' in a TypeScript template string was being interpreted
as a literal carriage return (\r), producing invalid shell syntax in the generated
Dockerfile. Escaping to '\\r' ensures the generated Dockerfile contains the
literal text '\r', correctly stripping Windows-style CRLF line endings from
entrypoint.sh.

INVARIANT: ∀ generated Dockerfile: sed pattern renders as 's/\r$//' in shell
PURITY: CORE - pure template transformation, no side effects

Fixes #151

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: konard

packages/lib/src/core/templates/dockerfile.ts

@@ -225,7 +225,7 @@ RUN mkdir -p ${config.targetDir} \
   && if [ "${config.targetDir}" != "/" ]; then chown -R 1000:1000 "${config.targetDir}"; fi
 
 COPY entrypoint.sh /entrypoint.sh
-RUN sed -i 's/\r$//' /entrypoint.sh && chmod +x /entrypoint.sh
+RUN sed -i 's/\\r$//' /entrypoint.sh && chmod +x /entrypoint.sh
 
 EXPOSE 22
 ENTRYPOINT ["/entrypoint.sh"]`