Standardize API request options

[wouter173]

Summary

• add typed request options for request bodies, path parameters, and query parameters
• centralize camelCase to snake_case encoding, including nested Schema.fromJsonString values
• migrate existing endpoints away from manual encoding and unnecessary Effect generators
• add focused coverage for body, query, and path encoding

Testing

• 74 tests pass
• formatting check passes
• lint passes
• diff check passes

Known issue

The repository typecheck still reports the two existing UrlParams.makeUrl errors in api/http-client/logging.ts. No changed file reports a type error.

Closes #17