feat(charts): validate post-processing options against operation schemas [DRAFT]

ChartDataPostProcessingOperationSchema accepted `options` as a free-form Dict;
the per-operation option schemas (aggregate, rolling, prophet, pivot, ...)
existed only for OpenAPI docs and were never wired into validation.

Add a validates_schema hook that maps each operation to its option schema and
validates `options` against it. Validation is lenient (unknown=EXCLUDE) so it
surfaces wrong types / out-of-range values on declared fields without rejecting
payloads that carry extra keys; operations without a dedicated schema are
unaffected.

DRAFT: these option schemas were never used for validation and have latent
issues (e.g. ChartDataAggregateOptionsSchema.groupby is accidentally a tuple,
so it isn't validated). Each option schema should be audited against the real
pandas_postprocessing signatures before strict (unknown=RAISE) validation is
considered, to avoid rejecting currently-valid requests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>