feat: add MongoDB Client-Side Field Level Encryption support

[gispada]

Description

This PR adds first-class support for MongoDB Client-Side Field Level Encryption (CSFLE) to Flowerbase, enabling sensitive data to be protected transparently at the application boundary.

With this feature, teams can define encryption intent directly in their collection schema configuration and let Flowerbase handle the operational complexity during startup. The platform now supports secure field-level encryption across both simple and nested document structures, making it easier to adopt strong data protection patterns without rewriting business logic.

List of proposed changes

• CSFLE setup flow in setupMongoDbCSFLE
• Recursive alias resolution for schema properties and nested objects
• Key vault index/key management for keyAltNames
• mongodbEncryptionConfig support in initialize(...)
• Unit tests for buildSchemaMap key alias resolution, including nested paths
• README documentation for feature behavior and configuration examples

Modified packages

• flowerbase
• demo