feat(14.1-01): add OAuth identities table and empty-list Index

- Model golem15_user_oauth_identities with Encrypted tokens and empty Fillable
- gormigrate 202610050001 with both unique indexes, cascade FK, and jsonb profile_data
- OAuthIdentitiesIndex returns {"data":[]} for a signed-in caller with no rows

updates/202610050001_create_oauth_identities.go

@@ -0,0 +1,36 @@
+package updates
+
+import (
+	"github.com/go-gormigrate/gormigrate/v2"
+	"gorm.io/gorm"
+)
+
+var oauthIdentityMigrations = []*gormigrate.Migration{
+	{
+		ID: "202610050001_create_oauth_identities",
+		Migrate: func(tx *gorm.DB) error {
+			return execStmts(tx, []string{
+				`CREATE TABLE golem15_user_oauth_identities (
+	id SERIAL PRIMARY KEY,
+	user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+	provider VARCHAR(50) NOT NULL,
+	provider_id VARCHAR(255) NOT NULL,
+	access_token TEXT NULL,
+	refresh_token TEXT NULL,
+	token_expires_at TIMESTAMPTZ NULL,
+	profile_data jsonb NULL,
+	linked_at TIMESTAMPTZ NULL,
+	created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+)`,
+				`CREATE UNIQUE INDEX oauth_identities_user_provider_unique ON golem15_user_oauth_identities (user_id, provider)`,
+				`CREATE UNIQUE INDEX oauth_identities_provider_identity_unique ON golem15_user_oauth_identities (provider, provider_id)`,
+			})
+		},
+		Rollback: func(tx *gorm.DB) error {
+			return tx.Exec("DROP TABLE IF EXISTS golem15_user_oauth_identities").Error
+		},
+	},
+}
+
+func init() { Register(oauthIdentityMigrations...) }