feat: add processor option to enable/disable OpenAPI export

[soulcodingmatt]

Task

Add a compiler option (-Aequilibrium.openapi.enabled=true) to control whether OpenAPI schema generation is active.

Parent story: #12
Parent epic: #18

Details

• Add option parsing in EquilibriumConfig
• Add openapi.outputDir option for schema output location (default: target/generated-schemas)
• When disabled (default), no OpenAPI processing occurs
• When enabled, the OpenAPI generator runs after DTO generation

Acceptance Criteria

• Option -Aequilibrium.openapi.enabled=true activates schema generation
• Option -Aequilibrium.openapi.outputDir=<path> controls output location
• By default, OpenAPI generation is disabled
• Options are documented in EquilibriumConfig