add script timeout, integration tests, and cleanup dead code

[ncode]

• Add configurable timeout for script execution (default 30s) to prevent hangs from misbehaving scripts. Uses exec.CommandContext internally.

• Remove unused excludeTagged() function and its test - dead code from previous refactor, functionality already exists in needsTag().

• Remove duplicate comment on getService() function.

• Add integration test suite with 8 tests covering:

  • Basic tag update cycle
  • Tag cleanup
  • Run loop with dynamic tags
  • Real script execution
  • Service not found error handling
  • Empty script output (removes all prefixed tags)
  • Idempotency (no unnecessary Consul writes)
  • Service metadata preservation

• Add docker-compose.test.yml with Consul 1.20 for local testing

• Add Makefile with targets: test, test-integration, consul-up/down

• Update CI workflow to run integration tests with Consul service container

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.75%. Comparing base (e728899) to head (091044c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   89.18%   89.75%   +0.56%     
==========================================
  Files           8        8              
  Lines         444      361      -83     
==========================================
- Hits          396      324      -72     
+ Misses         36       25      -11     
  Partials       12       12              

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