fix(stirling-pdf-logs): add support for Stirling-PDF 2.9.2+ log format

[Copilot]

Stirling-PDF 2.9.2+ changed the failed-login log format: the emitting class changed from CustomAuthenticationFailureHandler to AuthController, the level dropped from ERROR to WARN, and the message structure changed from Failed login attempt from IP: [X] to Invalid password for user: X from IP: Y.

Changes

• parsers/s01-parse/crowdsecurity/stirling-pdf-logs.yaml: adds a second grok node alongside the existing one to match the new format, preserving backwards compatibility:

- grok:
    pattern: "%{TIMESTAMP_ISO8601:timestamp} %{WORD:log_level} %{DATA:logger} \\[%{DATA:thread}\\] Invalid password for user: %{DATA:username} from IP: %{IP:source_ip}"
    apply_on: message
  statics:
    - meta: log_type
      value: failed_authentication

• .tests/stirling-pdf-logs/stirling-pdf.log: adds three new-format log samples (private IPs).
• .tests/stirling-pdf-logs/parser.assert: updated to cover the 3 additional entries across all parser stages (s00-raw, s01-parse, s02-enrich).

Checklist

• I have read the contributing guide
• I have tested my changes locally
• For new parsers or scenarios, tests have been added
• I have run the hub linter and no issues were reported (see contributing guide)
• Automated tests are passing
• AI was used to generate any/all content of this PR