fix: require users to authenticate existing Immich account before OAuth linking

open-api/immich-openapi-specs.json

@@ -7448,7 +7448,7 @@
           "content": {
             "application/json": {
               "schema": {
-                "$ref": "#/components/schemas/OAuthCallbackDto"
+                "$ref": "#/components/schemas/OAuthLinkDto"
               }
             }
           },
@@ -19116,6 +19116,27 @@
         ],
         "type": "object"
       },
+      "OAuthLinkDto": {
+        "properties": {
+          "codeVerifier": {
+            "description": "OAuth code verifier (PKCE)",
+            "type": "string"
+          },
+          "linkToken": {
+            "description": "OAuth link token from prior callback",
+            "type": "string"
+          },
+          "state": {
+            "description": "OAuth state parameter",
+            "type": "string"
+          },
+          "url": {
+            "description": "OAuth callback URL",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
       "OAuthTokenEndpointAuthMethod": {
         "description": "OAuth token endpoint auth method",
         "enum": [