Use GraphQL types directly for query variables instead of serde JSON

The wire shape of a query variable is defined twice: the client writes it with serde (#[serde(rename)], custom Serialize impls) and the server reads it with async-graphql (#[graphql(name)], Scalar/InputObject derives). Nothing ties the two together, so they are kept in step by hand.

The clearest cost is GqlTimeInput, which needs ~90 lines of hand-written Serialize/Deserialize purely to imitate what its Scalar derive already knows (serde would emit {"Simple": 5}; the server wants a bare 5). Alongside that there are 19 #[serde(rename)] attributes across the model types and 5 golden tests whose only job is catching drift between the two definitions.

This is a maintenance problem rather than a correctness one: the goldens and the e2e/parity suites (which push real filters through a real server) already catch drift today.

What blocks the obvious fix

Rendering variables through the GraphQL machinery would make the two directions inverse by construction, but the render half only exists for scalars:

So the work is: add a ToValue derive (locally, or upstream in dynamic-graphql) mirroring the field metadata the InputObject/OneOfInput derives already carry, then migrate the variable path off serde.

Landmine already defused

GqlTimeInput::to_value used to render Indexed(t, event_id) as a bare t, silently dropping the locked event id — the same loss fixed in 2c264835f. It is now the true inverse of from_value and pinned by round-trip tests, so a future migration to to_value will not reintroduce it. The other scalars' to_value impls should get the same round-trip check before being relied on.

Raised in review: https://github.com/Pometry/Raphtory/pull/2675#discussion_r3812162014

Start by tracing the query-variable serialization path and reading the existing ScalarValue::to_value and FromValue implementations, including GqlTimeInput and its round-trip tests. Then inspect the metadata produced by the InputObject and OneOfInput derives. Done means adding ToValue support for input objects and oneOf types, migrating variables off serde, and keeping the golden, e2e/parity, and scalar round-trip tests passing.