chore(studio): drop @supabase/postgres-meta in favor of @supabase/pg-meta (#45844)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

## What kind of change does this PR introduce?

Refactor / dependency cleanup.

## What is the current behavior?

`apps/studio` lists both `@supabase/pg-meta` (workspace package) as a
runtime dep and `@supabase/postgres-meta` (external npm package,
`^0.64.4`) as a devDependency. The external package is used only for
type imports across 44 files — there is no runtime usage and no codegen
pipeline that needs it.

## What is the new behavior?

Every `Postgres*` type import (`PostgresTable`, `PostgresColumn`,
`PostgresPolicy`, `PostgresTrigger`, `PostgresView`,
`PostgresMaterializedView`, `PostgresForeignTable`, `PostgresSchema`,
`PostgresPublication`, `PostgresRelationship`, `PostgresPrimaryKey`) is
replaced with its `PG*` counterpart from `@supabase/pg-meta`, and the
external dep is removed from \`apps/studio/package.json\`. Top-level
type re-exports were added to \`packages/pg-meta/src/index.ts\` so
consumers can import directly from the package root.

Two latent issues surfaced by the stricter pg-meta types are also fixed:
- \`data/foreign-tables/foreign-tables-query.ts\` was casting
foreign-table results as \`PostgresView[]\`; corrected to
\`PGForeignTable[]\`.
- \`pg-meta\`'s \`PGTrigger\` Zod schema declared
\`orientation\`/\`activation\` as \`z.string()\`, inconsistent with
pg-meta's own \`getDatabaseTriggerUpdateSQL\` helper that requires the
narrow literal unions; tightened to \`z.enum\`.

## Additional context

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated internal TypeScript type definitions across the codebase to
use the latest type system from `@supabase/pg-meta`.
  * Removed `@supabase/postgres-meta` dependency.
* Enhanced type validation for database triggers and schemas to enforce
stricter constraints.

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Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/supabase/supabase/pull/45844)

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apps/studio/package.json

@@ -151,7 +151,6 @@
     "@graphql-typed-document-node/core": "^3.2.0",
     "@radix-ui/react-use-escape-keydown": "^1.1.1",
     "@smithy/property-provider": "^4.0.4",
-    "@supabase/postgres-meta": "^0.64.4",
     "@testing-library/dom": "^10.0.0",
     "@testing-library/jest-dom": "^6.6.0",
     "@testing-library/react": "^16.0.0",