feat: add AI Bridge request logs model filter (#22230)

This pull-request implements a simple filtering logic so that we're able
to pick which model the user actually used when logs were sent to AI
Bridge.

- Add `GET /aibridge/models` API endpoint that returns distinct model
names from AI Bridge interceptions, with pagination and search support
- New `ListAIBridgeModels` SQL query using case-sensitive prefix
matching (`LIKE model || '%'`) to allow B-tree index usage
- Hand-written `ListAuthorizedAIBridgeModels` in `modelqueries.go` for
RBAC authorization filter injection
- `AIBridgeModels` search query parser in searchquery/search.go
(defaults bare terms to the `model` field)
- dbauthz wrappers, dbmetrics, and dbmock implementations for the new
query

<img width="292" height="185" alt="image"
src="https://github.com/user-attachments/assets/134771df-2d26-4c54-acc4-27f58128b351"
/>

coderd/searchquery/search.go

@@ -401,6 +401,35 @@ func AIBridgeInterceptions(ctx context.Context, db database.Store, query string,
 	return filter, parser.Errors
 }
 
+func AIBridgeModels(query string, page codersdk.Pagination) (database.ListAIBridgeModelsParams, []codersdk.ValidationError) {
+	// nolint:exhaustruct // Empty values just means "don't filter by that field".
+	filter := database.ListAIBridgeModelsParams{
+		// #nosec G115 - Safe conversion for pagination offset which is expected to be within int32 range
+		Offset: int32(page.Offset),
+		// #nosec G115 - Safe conversion for pagination limit which is expected to be within int32 range
+		Limit: int32(page.Limit),
+	}
+
+	if query == "" {
+		return filter, nil
+	}
+
+	values, errors := searchTerms(query, func(term string, values url.Values) error {
+		// Defaults to the `model` if no `key:value` pair is provided.
+		values.Add("model", term)
+		return nil
+	})
+	if len(errors) > 0 {
+		return filter, errors
+	}
+
+	parser := httpapi.NewQueryParamParser()
+	filter.Model = parser.String(values, "", "model")
+
+	parser.ErrorExcessParams(values)
+	return filter, parser.Errors
+}
+
 // Tasks parses a search query for tasks.
 //
 // Supported query parameters: