Refactor secrets detection into pattern registry (#18)

Refactor secrets detection into pattern registry (#18)

* Add PatternDetector and DetectionResult interfaces for secrets detection registry

* Move all interfaces to patterns/types.ts and use the existing SecretesDetectionResult interface instead of the new DetectionResult

* Move pattern detection utility to new patterns/utils.ts module

* Refactor secrets detection using a registry system

- Create privateKeysDetector, apiKeysDetector, tokensDetector modules
- Refactor detectSecrets() to use the pattern registry
- Re-export types from detect.ts for backwards compatibility

* Change default secrets_detection action to redaction

Hint: The example config still shows `action: block` explicitly, with a comment noting
that `redact` is the default action if not specified

* Fix README default action references and improve overall structure / formatting

- Update all references from 'block (default)' to 'redact (default)'
- Fix Bearer token documentation (20+ → 40+ chars)
- Reorganize Configuration section with consistent headers
- Improve table formatting and section descriptions
- Use references to reduce duplications and maintenance overhead

* Improve type safety in PatternDetector interface

Use SecretEntityType instead of string for enabledTypes Set parameter

* Update docs to reflect redact as new default action

Reorder actions to show default first

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Co-authored-by: Stefan Gasser <redacted>