feat: generate custom coverage config to omit legacy and external compoents (#9221)

* feat: generate custom coverage config to omit legacy and external components

* lint

* fix components config

* also remove deactivated componenets

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

scripts/generate_coverage_config.md

@@ -0,0 +1,36 @@
+# Dynamic Coverage Configuration
+
+This script generates a custom `.coveragerc` file for backend testing that excludes:
+
+1. **Bundled components** - Components listed in `SIDEBAR_BUNDLES` from `src/frontend/src/utils/styleUtils.ts`
+2. **Legacy components** - Python files containing `legacy = True`
+
+## How it works
+
+1. **Reads frontend config**: Parses `styleUtils.ts` to extract bundled component names
+2. **Scans backend files**: Finds all `.py` files in `src/backend/base/langflow/components/` with `legacy = True`
+3. **Generates .coveragerc**: Creates exclusion patterns for pytest-cov
+
+## Usage
+
+### Local development
+```bash
+# Generate config and run tests
+python3 scripts/generate_coverage_config.py
+cd src/backend && python -m pytest --cov=src/backend/base/langflow --cov-config=.coveragerc
+```
+
+### CI Integration
+The script runs automatically in CI before backend tests via `.github/workflows/python_test.yml`.
+
+## Files affected
+
+- **Input**: `src/frontend/src/utils/styleUtils.ts` (SIDEBAR_BUNDLES)
+- **Input**: `src/backend/base/langflow/components/**/*.py` (legacy components)  
+- **Output**: `src/backend/.coveragerc` (auto-generated, in .gitignore)
+
+## Benefits
+
+- **Accurate coverage**: Focuses on actively maintained core code
+- **Dynamic updates**: Automatically adapts when bundles/legacy components change
+- **Codecov compatible**: Generated config works with both local testing and Codecov reporting