feat: add Vertex AI authentication support for provider API keys

- Add auth_type field to ProviderAPIKey model (api_key or vertex_ai)
- Implement Vertex AI OAuth token generation with service account
- Update transport layer to handle Vertex AI authentication
- Add Vertex AI endpoint URL generation in request builder
- Update frontend KeyFormDialog to support auth_type selection
- Add migration for auth_type column in provider_api_keys table

alembic/versions/20260130_1000_add_auth_type_to_provider_api_keys.py

@@ -0,0 +1,51 @@
+"""Add auth_type and auth_config fields to provider_api_keys table
+
+Revision ID: 7f6f8065f517
+Revises: 364680d1bc99
+Create Date: 2026-01-30 10:00:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy import inspect
+
+# revision identifiers, used by Alembic.
+revision: str = "7f6f8065f517"
+down_revision: Union[str, None] = "364680d1bc99"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def column_exists(table_name: str, column_name: str) -> bool:
+    """检查列是否已存在"""
+    bind = op.get_bind()
+    inspector = inspect(bind)
+    columns = [col["name"] for col in inspector.get_columns(table_name)]
+    return column_name in columns
+
+
+def upgrade() -> None:
+    # 添加 auth_type 字段，默认值为 "api_key"
+    if not column_exists("provider_api_keys", "auth_type"):
+        op.add_column(
+            "provider_api_keys",
+            sa.Column("auth_type", sa.String(20), nullable=False, server_default="api_key"),
+        )
+
+    # 添加 auth_config 字段（Text，存储加密后的认证配置）
+    if not column_exists("provider_api_keys", "auth_config"):
+        op.add_column(
+            "provider_api_keys",
+            sa.Column("auth_config", sa.Text, nullable=True),
+        )
+
+
+def downgrade() -> None:
+    if column_exists("provider_api_keys", "auth_config"):
+        op.drop_column("provider_api_keys", "auth_config")
+
+    if column_exists("provider_api_keys", "auth_type"):
+        op.drop_column("provider_api_keys", "auth_type")