fix(docker): ensure uv is accessible in system PATH

Symlink uv from /root/.cargo/bin to /usr/local/bin to make it
accessible without relying on ENV PATH setting. Add version check
to verify successful installation during build.

Changes:
- Symlink uv to /usr/local/bin/uv
- Add 'uv --version' validation step
- Remove ENV PATH setting (no longer needed)

Fixes: uv: not found error in test script

Dockerfile.full

@@ -30,9 +30,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   python3-venv \
   && rm -rf /var/lib/apt/lists/*
 
-# Install uv
-RUN curl -LsSf https://astral.sh/uv/install.sh | sh
-ENV PATH="/root/.cargo/bin:$PATH"
+# Install uv and symlink to system path
+RUN curl -LsSf https://astral.sh/uv/install.sh | sh && \
+    ln -s /root/.cargo/bin/uv /usr/local/bin/uv && \
+    uv --version
 
 # Copy binary
 COPY --from=builder /src/build/picoclaw /usr/local/bin/picoclaw