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/querier.go

@@ -6,6 +6,7 @@ package database
 
 import (
 	"context"
+	"database/sql"
 	"encoding/json"
 	"time"
 
@@ -70,6 +71,11 @@ type sqlcQuerier interface {
 	// created_at ASC flows through to dbpurge's digest truncation; see
 	// buildDigestData in dbpurge.go for the tradeoff rationale.
 	AutoArchiveInactiveChats(ctx context.Context, arg AutoArchiveInactiveChatsParams) ([]AutoArchiveInactiveChatsRow, error)
+	// 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.
+	BackfillChatModelConfigProvider(ctx context.Context, arg BackfillChatModelConfigProviderParams) (sql.Result, error)
 	BackoffChatDiffStatus(ctx context.Context, arg BackoffChatDiffStatusParams) error
 	BatchUpdateWorkspaceAgentMetadata(ctx context.Context, arg BatchUpdateWorkspaceAgentMetadataParams) error
 	BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg BatchUpdateWorkspaceLastUsedAtParams) error