fix(pg-meta): include schema in pg_indexes join to avoid cross-schema index collisions (supabase#45374)

## I have read the CONTRIBUTING.md file.

YES

## What kind of change does this PR introduce?

Bug fix

## What is the current behavior?

The query in `sql/indexes.ts` joins `pg_class` with `pg_indexes` using
only the index name:

```sql
JOIN pg_indexes ix ON c.relname = ix.indexname
```

This can lead to incorrect results when multiple schemas contain indexes
with the same name. PostgreSQL allows identical index names across
different schemas, so this join may return the wrong index_definition.

## What is the new behavior?

The join condition now includes the schema name:

```sql
JOIN pg_indexes ix 
  ON c.relname = ix.indexname 
  AND n.nspname = ix.schemaname
```

This ensures the correct index_definition is retrieved for each index,
even when duplicate index names exist across schemas.

## Additional context

- Added a test case to verify behavior when the same index name exists
in multiple schemas.
- This change prevents cross-schema collisions and ensures accurate
index metadata retrieval.

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

* **Bug Fixes**
* Improved index listing so indexes that share the same name in
different schemas are correctly distinguished and reported.

* **Tests**
* Added a regression test ensuring indexes with identical names in
separate schemas are both detected and contain expected schema-qualified
references.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Charis Lam <26616127+charislam@users.noreply.github.com>

Author: Akash504-ai

packages/pg-meta/src/sql/indexes.ts

@@ -39,7 +39,7 @@ export const INDEXES_SQL = /* SQL */ safeSql`
     JOIN pg_namespace n ON c.relnamespace = n.oid
     JOIN pg_am am ON c.relam = am.oid
     JOIN pg_attribute a ON a.attrelid = c.oid AND a.attnum = ANY(idx.indkey)
-    JOIN pg_indexes ix ON c.relname = ix.indexname
+    JOIN pg_indexes ix ON c.relname = ix.indexname AND n.nspname = ix.schemaname
   GROUP BY
     idx.indexrelid, idx.indrelid, n.nspname, idx.indnatts, idx.indnkeyatts, idx.indisunique, 
     idx.indisprimary, idx.indisexclusion, idx.indimmediate, idx.indisclustered, idx.indisvalid, 

packages/pg-meta/test/indexes.test.ts

@@ -166,3 +166,35 @@ withTestDatabase('list with filters', async ({ executeQuery }) => {
   const offset = offsetZod.parse(await executeQuery(offsetSql))
   expect(offset).toHaveLength(withoutSystem.length - 1)
 })
+
+withTestDatabase('handles same index name across schemas correctly', async ({ executeQuery }) => {
+  // Create two schemas
+  await executeQuery(`CREATE SCHEMA schema_a;`)
+  await executeQuery(`CREATE SCHEMA schema_b;`)
+
+  // Create tables
+  await executeQuery(`CREATE TABLE schema_a.test (id int);`)
+  await executeQuery(`CREATE TABLE schema_b.test (id int);`)
+
+  // Create SAME index name in both schemas
+  await executeQuery(`CREATE INDEX idx_test ON schema_a.test (id);`)
+  await executeQuery(`CREATE INDEX idx_test ON schema_b.test (id);`)
+
+  // Fetch indexes
+  const { sql, zod } = await pgMeta.indexes.list({ includeSystemSchemas: true })
+  const indexes = zod.parse(await executeQuery(sql))
+
+  const schemaAIndex = indexes.find(
+    (i) => i.schema === 'schema_a' && i.index_definition.includes('schema_a.test')
+  )
+
+  const schemaBIndex = indexes.find(
+    (i) => i.schema === 'schema_b' && i.index_definition.includes('schema_b.test')
+  )
+
+  expect(schemaAIndex).toBeDefined()
+  expect(schemaBIndex).toBeDefined()
+
+  expect(schemaAIndex!.index_definition).toContain('schema_a.test')
+  expect(schemaBIndex!.index_definition).toContain('schema_b.test')
+})