Wasm Synth module registry

GET  /v1/index.json        full catalog (mods + chains)
GET  /v1/search?q=term     filtered catalog
GET  /v1/download/<id>     module .wasm bytes
GET  /v1/chains/<id>       chain manifest JSON
PUT  /v1/modules/<id>      publish a mod (Bearer token)
DELETE /v1/modules/<id>    remove a mod (Bearer token)
PUT  /v1/chains/<id>       publish a chain (Bearer token)
DELETE /v1/chains/<id>     remove a chain (Bearer token)