feat(meta-schema): expose i18n and realtime metadata in _meta query

[pyramation]

Summary

Extends the _meta schema plugin to expose i18n and realtime metadata on MetaTable, continuing the pattern from storage/search (#1298) and enums (#1299).

i18n — tables tagged with @i18n <translation_table> now expose:

i18n {
  translationTable    # "post_translations"
  translatableFields { name type }  # [{name: "title", type: "text"}, ...]
}

Detection: reads codec.extensions.tags.i18n, then intersects the base table's text/citext columns with the translation table's attributes to produce the translatableFields list.

Realtime — tables tagged with @realtime now expose:

realtime {
  subscriptionFieldName  # "onPostChanged"
}

Detection: checks codec.extensions.tags.realtime, derives the subscription field name via on${tableType}Changed.

Both return null for tables without the respective tag. Adds buildI18nMeta() and buildRealtimeMeta() in storage-search-meta-builders.ts, new GraphQL types (MetaI18n, MetaI18nField, MetaRealtime), 6 unit tests, and updated introspection/schema snapshots.

Link to Devin session: https://app.devin.ai/sessions/c93bb5e1b114421196d8eb28435b0515
Requested by: @pyramation

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