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>

turbo.json

@@ -1,6 +1,35 @@
 {
   "$schema": "https://turborepo.dev/schema.json",
   "globalEnv": ["CI", "DATABASE_URL", "PAYLOAD_SECRET", "NODE_ENV"],
+  "boundaries": {
+    "tags": {
+      "app": {
+        "dependencies": {
+          "allow": ["app", "core", "core-composition", "feature", "tooling"]
+        }
+      },
+      "feature": {
+        "dependencies": {
+          "allow": ["core", "tooling"]
+        }
+      },
+      "core": {
+        "dependencies": {
+          "allow": ["core", "core-composition", "tooling"]
+        }
+      },
+      "core-composition": {
+        "dependencies": {
+          "allow": ["core", "feature", "tooling"]
+        }
+      },
+      "tooling": {
+        "dependencies": {
+          "allow": ["tooling"]
+        }
+      }
+    }
+  },
   "tasks": {
     "build": {
       "dependsOn": ["^build"],