Fix Docker lock file: use wheel-compatible dependency resolution

- Generate uv.docker.lock with wheel-based gsplat dependency
- Update Dockerfile to use Docker-specific lock file
- This resolves 'Distribution not found at: file:///home/user/app/gsplat' error
- Lock file now matches the wheel path used in pyproject.docker.toml

Dockerfile

@@ -44,7 +44,7 @@ ENV HOME=/home/user \
 
 # Copy dependency files with exact versions
 COPY --chown=user pyproject.docker.toml ./pyproject.toml
-COPY --chown=user uv.lock ./uv.lock
+COPY --chown=user uv.docker.lock ./uv.lock
 
 # Download optimized gsplat wheel (built with same PyTorch version)
 RUN mkdir -p wheels && \