build(turbo): add boundaries enforcement matching ESLint dependency graph

Per-package tags + root boundaries block now enforce the same three-tag
model as eslint-plugin-boundaries:
- app          → may depend on: app, core, core-composition, feature, tooling
- feature      → may depend on: core, tooling
- core         → may depend on: core, core-composition, tooling
- core-composition (core-api, core-cms) → may depend on: core, feature, tooling
- tooling (core-eslint, core-typescript) → may depend on: tooling

Tags applied: 4 apps (app), 3 core foundation packages (core),
2 core composition packages (core-composition), 5 features (feature),
2 tooling packages (tooling). All test suites pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web-next/turbo.json

@@ -0,0 +1,4 @@
+{
+  "extends": ["//"],
+  "tags": ["app"]
+}