fix duplicate key error during db migration

[lichao127]

This PR fixes the duplicate key value violates unique constraint "pg_extension_name_index" error during the db migration step in ./install.sh.

Expand for full error message:

⏳ Running migrations...
Applied migration: 0000_yielding_bloodaxe.sql
❌ Migration failed
PostgresError: duplicate key value violates unique constraint "pg_extension_name_index"
    at ErrorResponse (/Users/lichao127/HistoryRAG/node_modules/.pnpm/postgres@3.4.4/node_modules/postgres/cjs/src/connection.js:788:26)
    at handle (/Users/lichao127/HistoryRAG/node_modules/.pnpm/postgres@3.4.4/node_modules/postgres/cjs/src/connection.js:474:6)
    at Socket.data (/Users/lichao127/HistoryRAG/node_modules/.pnpm/postgres@3.4.4/node_modules/postgres/cjs/src/connection.js:315:9)
    at Socket.emit (node:events:507:28)
    at addChunk (node:internal/streams/readable:559:12)
    at readableAddChunkPushByteMode (node:internal/streams/readable:510:3)
    at Readable.push (node:internal/streams/readable:390:5)
    at TCP.onStreamRead (node:internal/stream_base_commons:189:23) {
  severity_local: 'ERROR',
  severity: 'ERROR',
  code: '23505',
  detail: 'Key (extname)=(vector) already exists.',
  schema_name: 'pg_catalog',
  table_name: 'pg_extension',
  constraint_name: 'pg_extension_name_index',
  file: 'nbtinsert.c',
  line: '673',
  routine: '_bt_check_unique'
}
 ELIFECYCLE  Command failed with exit code 1.