fix: manual refresh returns 0 tools for Authorization Code OAuth gateways

[ecthelion77]

Bug Description

The POST /gateways/{id}/tools/refresh endpoint silently returns 0 tools for OAuth gateways using the authorization_code grant type. The response completes in ~5ms with all counts at zero, without ever connecting to the upstream MCP server.

Meanwhile, the POST /oauth/fetch-tools/{id} endpoint works correctly for the same gateway.

Root Cause

_initialize_gateway() has an early-return path (around L4060-4073 in gateway_service.py) that skips MCP server connection when:

• auth_type == "oauth"
• grant_type == "authorization_code"
• oauth_auto_fetch_tool_flag == False (the default)

The refresh_gateway_manually() method never retrieves the stored OAuth token from TokenStorageService, so pre_auth_headers is empty and the early-return path is always triggered.

This is inconsistent with:

1. The health check code path, which correctly retrieves the stored user token via TokenStorageService.get_user_token() before connecting
2. The fetch_tools_after_oauth() method, which also retrieves the stored token and constructs {"Authorization": f"Bearer {access_token}"} before connecting

Steps to Reproduce

1. Create a gateway with auth_type: oauth, grant_type: authorization_code
2. Complete the OAuth authorization flow (user gets redirected and token is stored)
3. Call POST /gateways/{id}/tools/refresh
4. Response: {"toolsAdded": 0, "toolsUpdated": 0, "toolsRemoved": 0} in ~5ms
5. Call POST /oauth/fetch-tools/{id} — returns tools correctly

Impact

• Manual tool refresh from the admin UI never works for Authorization Code OAuth gateways
• Only /oauth/fetch-tools/ works, which is a separate endpoint not used by the standard refresh button
• Scheduled auto-refresh from health checks works (it retrieves the token), but manual refresh does not

Proposed Fix

In refresh_gateway_manually(), when the gateway uses authorization_code OAuth flow and the caller has a user_email, retrieve the stored access token from TokenStorageService and inject it into pre_auth_headers. This causes _initialize_gateway() to use pre_auth_headers directly, bypassing the authorization_code early-return path.

PR: forthcoming