chore(server): drop unused postgresCredentials feature (#20573)

## Summary

Drops the `postgresCredentials` legacy feature: a never-finished
"postgres proxy" that would have let users query their workspace data
over a standard Postgres connection. Nothing — frontend, e2e, Zapier,
docs, other server code — calls these mutations/query.

## History

- **Introduced** June 2024 (#5767, Thomas Trompette) as "first step for
creating credentials for database proxy", alongside the Postgres FDW /
remote-server work and the custom `twenty-postgres-spilo` image. Planned
follow-ups (provisioning a DB on the proxy, mapping users, exposing it
as a remote server) never landed.
- **Abandoned** January 2026 (#17001, Weiko) when the sibling "remote
integration" feature was removed as a BREAKING CHANGE — "not maintained
for more than a year and never officially launched". The spilo image was
then replaced with vanilla `postgres:16` (#19182, March 2026), retiring
the FDW infrastructure entirely.
- This PR finishes the cleanup: removes the orphaned module, the
`allPostgresCredentials` relation, `JwtTokenTypeEnum.POSTGRES_PROXY` +
payload, the reserved metadata keywords, and adds a 2.5.0 fast instance
command that drops `core.postgresCredentials` (reversible `down`).
Regenerated frontend GraphQL types + SDK metadata client.

## Test plan

- [x] `tsgo --noEmit` clean on twenty-server + twenty-front; lint +
prettier clean on touched files.
- [x] `database:migrate:generate` reports no pending schema diff; server
boots and serves the new schema.

packages/twenty-client-sdk/src/metadata/generated/schema.graphql

@@ -2443,13 +2443,6 @@ type ImapSmtpCaldavConnectionSuccess {
   connectedAccountId: String!
 }
 
-type PostgresCredentials {
-  id: UUID!
-  user: String!
-  password: String!
-  workspaceId: UUID!
-}
-
 type ToolIndexEntry {
   name: String!
   description: String!
@@ -3062,7 +3055,6 @@ type Query {
   getAutoCompleteAddress(address: String!, token: String!, country: String, isFieldCity: Boolean): [AutocompleteResult!]!
   getAddressDetails(placeId: String!, token: String!): PlaceDetailsResult!
   getUsageAnalytics(input: UsageAnalyticsInput): UsageAnalytics!
-  getPostgresCredentials: PostgresCredentials
   findManyPublicDomains: [PublicDomain!]!
   getEmailingDomains: [EmailingDomain!]!
   findManyMarketplaceApps: [MarketplaceApp!]!
@@ -3334,8 +3326,6 @@ type Mutation {
   startChannelSync(connectedAccountId: UUID!): ChannelSyncSuccess!
   saveImapSmtpCaldavAccount(accountOwnerId: UUID!, handle: String!, connectionParameters: EmailAccountConnectionParameters!, id: UUID): ImapSmtpCaldavConnectionSuccess!
   updateLabPublicFeatureFlag(input: UpdateLabPublicFeatureFlagInput!): FeatureFlag!
-  enablePostgresProxy: PostgresCredentials!
-  disablePostgresProxy: PostgresCredentials!
   createPublicDomain(domain: String!, applicationId: String): PublicDomain!
   updatePublicDomain(domain: String!, applicationId: String): PublicDomain!
   deletePublicDomain(domain: String!): Boolean!

packages/twenty-client-sdk/src/metadata/generated/schema.ts

@@ -2124,14 +2124,6 @@ export interface ImapSmtpCaldavConnectionSuccess {
     __typename: 'ImapSmtpCaldavConnectionSuccess'
 }
 
-export interface PostgresCredentials {
-    id: Scalars['UUID']
-    user: Scalars['String']
-    password: Scalars['String']
-    workspaceId: Scalars['UUID']
-    __typename: 'PostgresCredentials'
-}
-
 export interface ToolIndexEntry {
     name: Scalars['String']
     description: Scalars['String']
@@ -2665,7 +2657,6 @@ export interface Query {
     getAutoCompleteAddress: AutocompleteResult[]
     getAddressDetails: PlaceDetailsResult
     getUsageAnalytics: UsageAnalytics
-    getPostgresCredentials?: PostgresCredentials
     findManyPublicDomains: PublicDomain[]
     getEmailingDomains: EmailingDomain[]
     findManyMarketplaceApps: MarketplaceApp[]
@@ -2870,8 +2861,6 @@ export interface Mutation {
     startChannelSync: ChannelSyncSuccess
     saveImapSmtpCaldavAccount: ImapSmtpCaldavConnectionSuccess
     updateLabPublicFeatureFlag: FeatureFlag
-    enablePostgresProxy: PostgresCredentials
-    disablePostgresProxy: PostgresCredentials
     createPublicDomain: PublicDomain
     updatePublicDomain: PublicDomain
     deletePublicDomain: Scalars['Boolean']
@@ -5158,15 +5147,6 @@ export interface ImapSmtpCaldavConnectionSuccessGenqlSelection{
     __scalar?: boolean | number
 }
 
-export interface PostgresCredentialsGenqlSelection{
-    id?: boolean | number
-    user?: boolean | number
-    password?: boolean | number
-    workspaceId?: boolean | number
-    __typename?: boolean | number
-    __scalar?: boolean | number
-}
-
 export interface ToolIndexEntryGenqlSelection{
     name?: boolean | number
     description?: boolean | number
@@ -5730,7 +5710,6 @@ export interface QueryGenqlSelection{
     getAutoCompleteAddress?: (AutocompleteResultGenqlSelection & { __args: {address: Scalars['String'], token: Scalars['String'], country?: (Scalars['String'] | null), isFieldCity?: (Scalars['Boolean'] | null)} })
     getAddressDetails?: (PlaceDetailsResultGenqlSelection & { __args: {placeId: Scalars['String'], token: Scalars['String']} })
     getUsageAnalytics?: (UsageAnalyticsGenqlSelection & { __args?: {input?: (UsageAnalyticsInput | null)} })
-    getPostgresCredentials?: PostgresCredentialsGenqlSelection
     findManyPublicDomains?: PublicDomainGenqlSelection
     getEmailingDomains?: EmailingDomainGenqlSelection
     findManyMarketplaceApps?: MarketplaceAppGenqlSelection
@@ -5956,8 +5935,6 @@ export interface MutationGenqlSelection{
     startChannelSync?: (ChannelSyncSuccessGenqlSelection & { __args: {connectedAccountId: Scalars['UUID']} })
     saveImapSmtpCaldavAccount?: (ImapSmtpCaldavConnectionSuccessGenqlSelection & { __args: {accountOwnerId: Scalars['UUID'], handle: Scalars['String'], connectionParameters: EmailAccountConnectionParameters, id?: (Scalars['UUID'] | null)} })
     updateLabPublicFeatureFlag?: (FeatureFlagGenqlSelection & { __args: {input: UpdateLabPublicFeatureFlagInput} })
-    enablePostgresProxy?: PostgresCredentialsGenqlSelection
-    disablePostgresProxy?: PostgresCredentialsGenqlSelection
     createPublicDomain?: (PublicDomainGenqlSelection & { __args: {domain: Scalars['String'], applicationId?: (Scalars['String'] | null)} })
     updatePublicDomain?: (PublicDomainGenqlSelection & { __args: {domain: Scalars['String'], applicationId?: (Scalars['String'] | null)} })
     deletePublicDomain?: { __args: {domain: Scalars['String']} }
@@ -7975,14 +7952,6 @@ export interface LogicFunctionLogsInput {applicationId?: (Scalars['UUID'] | null
     
 
 
-    const PostgresCredentials_possibleTypes: string[] = ['PostgresCredentials']
-    export const isPostgresCredentials = (obj?: { __typename?: any } | null): obj is PostgresCredentials => {
-      if (!obj?.__typename) throw new Error('__typename is missing in "isPostgresCredentials"')
-      return PostgresCredentials_possibleTypes.includes(obj.__typename)
-    }
-    
-
-
     const ToolIndexEntry_possibleTypes: string[] = ['ToolIndexEntry']
     export const isToolIndexEntry = (obj?: { __typename?: any } | null): obj is ToolIndexEntry => {
       if (!obj?.__typename) throw new Error('__typename is missing in "isToolIndexEntry"')