Add swaggo/swag OpenAPI spec generation with /openapi.yaml endpoint

[Copilot]

• Explore codebase and understand structure
• Add swagger annotations to main.go and all handlers
• Run swag init to generate docs/ (docs.go, swagger.json, swagger.yaml)
• Create docs/embed.go to embed swagger.yaml at compile time
• Create handlers/openapi.go with GetOpenAPISpec handler serving GET /openapi.yaml
• Add OpenAPISpecPath constant to handlers/routes.go
• Create routers/openapi.go to register the /openapi.yaml route
• Update routers/routers.go to call the new openapi route group
• Add generate-docs recipe to justfile
• Update AGENTS.md with docs generation workflow documentation
• Update CI to install swag v1.16.4 and check docs are in sync
• Add handlers/openapi_test.go unit test for the new handler
• Fix: regenerate docs with exact swag v1.16.4 to match CI output (removed spurious format: float64 from rates additionalProperties)

[kamaal111]

@copilot you make sure the check openapi spec is in sync.
The pipeline is currently failing the step you just added

[Copilot]

@copilot you make sure the check openapi spec is in sync.
The pipeline is currently failing the step you just added

Fixed in a946c47. The docs were generated locally with a slightly different swag binary that included "format": "float64" in the rates additionalProperties, while CI's swag@v1.16.4 omits it. Regenerated with the exact same version (v1.16.4) so the committed docs now match what CI produces.