Add integration tests for dbt import with local dbt project

## Context
PR #5827 added dbt integration but lacks proper integration tests with an actual dbt project setup.

## Description
As mentioned by @franciscojavierarceo in PR #5827, we need a lightweight local dbt project that:
- Sets up a minimal dbt project structure
- Runs dbt compile to generate manifest.json
- Tests the full `feast dbt import` workflow end-to-end
- Validates generated Feast objects

## Acceptance Criteria
- [ ] Create test dbt project in `sdk/python/tests/integration/dbt/`
- [ ] Add test that compiles dbt project and imports to Feast
- [ ] Test all three data source types (bigquery, snowflake, file)
- [ ] Verify FeatureViews are created correctly
- [ ] Test tag filtering and model selection

## Related
- PR #5827
- Issue #3335