fix: smoke test leaks orphaned mock-forgejo.py processes (#196)

Add cleanup trap to smoke-init.sh that kills all mock-forgejo.py processes
on exit (success or failure). Also ensure cleanup at test start removes
any leftover processes from prior runs.

In .woodpecker/smoke-init.yml:
- Store the PID of the mock-forgejo.py background process
- Kill the process after smoke test completes

This prevents accumulation of orphaned Python processes that caused
OOM issues (2881 processes consuming 7.45GB RAM).

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

.woodpecker/smoke-init.yml

@@ -12,6 +12,7 @@ steps:
     image: python:3-alpine
     commands:
       - apk add --no-cache bash curl jq git coreutils
-      - python3 tests/mock-forgejo.py &
+      - python3 tests/mock-forgejo.py & echo $! > /tmp/mock-forgejo.pid
       - sleep 2
       - bash tests/smoke-init.sh
+      - kill $(cat /tmp/mock-forgejo.pid) 2>/dev/null || true