fix: backfill legacy Bedrock AI provider rows and stale model config strings (#26155)

Fixes CODAGT-548

Adds two idempotent startup backfills run after `newAPI():

- `BackfillBedrockProviderType`: promotes `ai_providers` rows from
`type=anthropic` with Bedrock settings to `type=bedrock`.
- `BackfillChatModelConfigProviderStrings`: fixes stale
`chat_model_configs.provider = "anthropic"` strings on rows whose linked
provider was just promoted.
- `UpdateAIProvider` query now also writes the `type` column, so the
fix persists on any subsequent PATCH.


> 🤖 Generated by Claude with oversight from a human.

coderd/database/queries/ai_providers.sql

@@ -66,6 +66,7 @@ RETURNING
 UPDATE
     ai_providers
 SET
+    type = @type::ai_provider_type,
     display_name = sqlc.narg('display_name')::text,
     enabled = @enabled::boolean,
     base_url = @base_url::text,

coderd/database/queries/chatmodelconfigs.sql

@@ -144,6 +144,27 @@ WHERE
     provider = @provider::text
     AND deleted = FALSE;
 
+-- name: BackfillChatModelConfigProvider :execresult
+-- old_provider is matched as text; new_provider is also cast to ai_provider_type
+-- for the EXISTS check against ai_providers.type.
+-- ai_provider_id IS NOT NULL is defensive; the check constraint already
+-- enforces that non-deleted rows always have a provider ID.
+UPDATE
+    chat_model_configs
+SET
+    provider   = @new_provider::text,
+    updated_at = NOW()
+WHERE
+    provider          = @old_provider::text
+    AND deleted       = FALSE
+    AND ai_provider_id IS NOT NULL
+    AND EXISTS (
+        SELECT 1 FROM ai_providers
+        WHERE  id      = chat_model_configs.ai_provider_id
+          AND  type    = @new_provider::ai_provider_type
+          AND  deleted = FALSE
+    );
+
 -- name: DeleteChatModelConfigsByAIProviderID :exec
 UPDATE
     chat_model_configs