fix: correct PUT /api/v1/provider silently dropping model_type, endpoint_url, encrypted_config (#1627)

[carlosjarenom]

Problem

ProviderService.update() uses a field whitelist that doesn't match the actual Provider ORM model fields:

Whitelist entry	Actual model field	Result
api_base	doesn't exist (real: endpoint_url)	dead code
extra_config	doesn't exist (real: encrypted_config)	dead code
(missing)	model_type	silently rejected
(missing)	endpoint_url	silently rejected
(missing)	encrypted_config	silently rejected

PUT /api/v1/provider/{id} returns 200 OK but silently drops updates to model_type, endpoint_url, and encrypted_config.

Fix

Replace the incorrect whitelist entries with the actual Provider field names:

# Before
_UPDATABLE_FIELDS = {"provider_name", "api_key", "api_base", "extra_config", "prefer", "is_vaild"}

# After
_UPDATABLE_FIELDS = {"provider_name", "model_type", "api_key", "endpoint_url", "encrypted_config", "prefer", "is_vaild"}

• api_base → endpoint_url
• extra_config → encrypted_config
• Added model_type (was missing)

Note: is_vaild typo is project-wide and kept as-is (out of scope).

Reproduction

1. Settings → Agent → Models → BYOK → create provider with claude-opus-4-6
2. Edit same provider, change model_type to gpt-4o, click Save → success toast
3. Run task → still uses Claude (DB unchanged)

Closes #1627