docs: implement Phase 2 - API documentation with TypeDoc

Set up TypeDoc to auto-generate comprehensive API reference documentation
from TypeScript source code.

Changes:
- Installed typedoc and typedoc-plugin-markdown (v0.2.0 plugins)
- Created typedoc.json configuration with 9 entry points
- Added docs:api and docs:watch npm scripts
- Fixed test file imports (validateNamespace → isValidNamespace)
- Updated tsconfig.json to exclude test files from compilation
- Generated markdown API documentation in docs/api-reference/generated/

Generated API documentation:
- 9 modules documented (lib/, hooks/, types/)
- lib/crypto - 14 encryption/certificate functions
- lib/controller - 5 Kubernetes API functions
- lib/validators - 6 validation functions
- lib/retry - Exponential backoff utilities
- lib/rbac - RBAC permission checking
- types - Result types, branded types, interfaces
- hooks/useSealedSecretEncryption - Encryption React hook
- hooks/usePermissions - RBAC React hooks
- hooks/useControllerHealth - Health monitoring hook

Benefits:
- Auto-generated from TypeScript source (stays in sync)
- Markdown format for easy integration
- Type signatures and JSDoc included
- Function parameters and return types documented
- Links between related types and functions

Phase 2 deliverables (2-3 days estimated, completed in 1 session):
✅ TypeDoc installed and configured
✅ Entry points identified for all core modules
✅ API documentation generated (9 modules, 40+ functions)
✅ npm scripts added for docs generation
✅ Test files excluded from documentation

Next: Phase 3 - User tutorials and guides

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

docs/api-reference/generated/lib/validators/functions/validateSecretKey.md

@@ -0,0 +1,27 @@
+[**Headlamp Sealed Secrets API v0.2.0**](../../../README.md)
+
+***
+
+[Headlamp Sealed Secrets API](../../../README.md) / [lib/validators](../README.md) / validateSecretKey
+
+# Function: validateSecretKey()
+
+> **validateSecretKey**(`key`): [`ValidationResult`](../interfaces/ValidationResult.md)
+
+Defined in: [src/lib/validators.ts:168](https://github.com/cpfarhood/headlamp-sealed-secrets-plugin/blob/bdf19cd3bf5a2d679b7ba949108fe9df1843c5f4/headlamp-sealed-secrets/src/lib/validators.ts#L168)
+
+Validate secret key name with detailed error message
+
+## Parameters
+
+### key
+
+`string`
+
+Key name to validate
+
+## Returns
+
+[`ValidationResult`](../interfaces/ValidationResult.md)
+
+Validation result with error message if invalid