Add plugin platform with modular backend and frontend registry.

Split graph/import/meta into Django apps, add API v1 with OpenAPI and pytest, and introduce plugin registry with the tags reference plugin on both FE and BE.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/pyproject.toml

@@ -0,0 +1,41 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "social-graph-backend"
+version = "1.0.0"
+description = "Social Graph Builder API"
+readme = "README.md"
+requires-python = ">=3.11"
+dependencies = [
+  "Django==4.2.9",
+  "djangorestframework==3.14.0",
+  "django-cors-headers==4.3.1",
+  "drf-spectacular==0.27.1",
+  "djangorestframework-simplejwt==5.3.1",
+  "Pillow==10.2.0",
+]
+
+[project.optional-dependencies]
+dev = ["pytest==8.0.0", "pytest-django==4.8.0"]
+
+[project.entry-points."social_graph.plugins"]
+tags = "plugins_tags.plugin:TagsPlugin"
+
+[tool.setuptools.packages.find]
+where = ["."]
+include = [
+  "config*",
+  "contacts*",
+  "core*",
+  "graph*",
+  "import_export*",
+  "plugins*",
+  "plugins_tags*",
+  "api*",
+]
+
+[tool.pytest.ini_options]
+DJANGO_SETTINGS_MODULE = "config.settings"
+python_files = ["tests.py", "test_*.py", "*_tests.py"]