feat: implement AtoCore Phase 0 + Phase 0.5 (foundation + PoC)

Complete implementation of the personal context engine foundation:
- FastAPI server with 5 endpoints (ingest, query, context/build, health, debug)
- SQLite database with 5 tables (documents, chunks, memories, projects, interactions)
- Heading-aware markdown chunker (800 char max, recursive splitting)
- Multilingual embeddings via sentence-transformers (EN/FR)
- ChromaDB vector store with cosine similarity retrieval
- Context builder with project boosting, dedup, and budget enforcement
- CLI scripts for batch ingestion and test prompt evaluation
- 19 unit tests passing, 79% coverage
- Validated on 482 real project files (8383 chunks, 0 errors)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -0,0 +1,36 @@
+[build-system]
+requires = ["setuptools>=68.0", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "atocore"
+version = "0.1.0"
+description = "Personal context engine for LLM interactions"
+requires-python = ">=3.11"
+dependencies = [
+    "fastapi>=0.110.0",
+    "uvicorn[standard]>=0.27.0",
+    "python-frontmatter>=1.1.0",
+    "chromadb>=0.4.22",
+    "sentence-transformers>=2.5.0",
+    "pydantic>=2.6.0",
+    "pydantic-settings>=2.1.0",
+    "structlog>=24.1.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.0.0",
+    "pytest-cov>=4.1.0",
+    "httpx>=0.27.0",
+    "pyyaml>=6.0.0",
+]
+
+[tool.setuptools.packages.find]
+where = ["src"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+python_files = ["test_*.py"]
+python_functions = ["test_*"]
+addopts = "--cov=atocore --cov-report=term-missing -v"