Catalog: Java BECs (no-printstacktrace, no-system-out-println)

[DataDave-Dev]

Part of #25 (one language per PR). No code required — a catalog BEC is a single YAML file using the generic forbid check.

Task

Add ready-to-import Java BECs under src/becwright/becs/:

• no-printstacktrace.bec.yaml — forbid .printStackTrace() (swallowed exceptions) in **/*.java.
• no-system-out-println.bec.yaml — forbid System.out.println debugging in main sources (consider excluding **/test/**).

How

1. Copy the format from src/becwright/becs/no-debug-go.bec.yaml.
2. Write a real intent and why_it_matters.
3. Use check: "becwright run forbid --pattern '...'" with paths **/*.java.
4. Add the entries to src/becwright/becs/README.md.

Acceptance criteria

• pytest green (test_catalog_bundles_are_valid covers bundle parsing).
• becwright add no-printstacktrace installs it in a scratch repo.

See CONTRIBUTING.md → "Adding a catalog BEC".