Update site builder configurations and enhance migration dependencies

- Added `OptimizationConfig` to `INSTALLED_APPS` in `settings.py`.
- Updated migration dependencies in `0001_initial.py` to include `writer` for content source fields.
- Modified the `account` ForeignKey in `PageBlueprint` and `SiteBlueprint` models to use `tenant_id` for better clarity.
- Deleted obsolete implementation plan documents for phases 0-4 to streamline project documentation.
- Improved overall project structure by removing outdated files and enhancing migration clarity.

backend/igny8_core/settings.py

@@ -53,6 +53,7 @@ INSTALLED_APPS = [
     'igny8_core.modules.billing.apps.BillingConfig',
     'igny8_core.modules.automation.apps.AutomationConfig',
     'igny8_core.business.site_building.apps.SiteBuildingConfig',
+    'igny8_core.business.optimization.apps.OptimizationConfig',
     'igny8_core.modules.site_builder.apps.SiteBuilderConfig',
     'igny8_core.modules.linker.apps.LinkerConfig',
     'igny8_core.modules.optimizer.apps.OptimizerConfig',