refactor(opencode): install opencode via npm instead of curl

- Replace curl-based installation with npm install -g opencode-ai
- Remove manual PATH setup and symlink creation
- Simplify installation process

Quality gates: code review

apps/api/src/main.py

@@ -168,16 +168,8 @@ services:
     ports:
       - "3000:3000"
     command: >
-      sh -c "apt-get update && apt-get install -y curl git tar &&
-             curl -fsSL https://opencode.ai/install | bash &&
-             OPCODE_BIN=$HOME/.opencode/bin/opencode &&
-             if [ -f $OPCODE_BIN ]; then
-               ln -sf $OPCODE_BIN /usr/local/bin/opencode
-               echo 'export PATH=\"$HOME/.opencode/bin:$PATH\"' >> /etc/profile
-               echo 'export PATH=\"$HOME/.opencode/bin:$PATH\"' >> /root/.bashrc
-             else
-               echo 'Warning: opencode binary not found at expected location'
-             fi &&
+      sh -c "apt-get update && apt-get install -y git &&
+             npm install -g opencode-ai &&
              mkdir -p /workspace &&
              echo 'OpenCode installed. Run: opencode' &&
              tail -f /dev/null"