Initial project scaffold: FastAPI backend + Svelte 5 frontend

Backend (uv): FastAPI app with routers (foods, log, targets, OFF proxy),
SQLAlchemy models, Pydantic schemas, migration runner + 0001 initial schema,
example pytest suite (7 tests).
Frontend (npm): Vite 7 + Svelte 5 runes, lib/ (api, stores, scanner, format)
per spec §7, placeholder components, example vitest suite (4 tests).
SPEC.md §1: registered uvicorn and Vitest (rule §8.3.3).

backend/database.py

@@ -0,0 +1,70 @@
+"""DB connection, session management, and migration runner (spec §8.1 rules 5 & 9)."""
+
+import os
+import re
+import sqlite3
+from pathlib import Path
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+
+DATABASE_URL = os.environ.get("CALCOUNT_DATABASE_URL", "sqlite:///./calcount.db")
+
+engine = create_engine(
+    DATABASE_URL,
+    # Required for SQLite with FastAPI's threadpool handlers (spec §8.1 rule 4)
+    connect_args={"check_same_thread": False},
+)
+SessionLocal = sessionmaker(bind=engine, autoflush=False, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_db():
+    """One DB session per request (spec §8.1 rule 5)."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+MIGRATIONS_DIR = Path(__file__).parent / "migrations"
+
+
+def run_migrations(db_path: str | None = None) -> None:
+    """Apply numbered SQL migrations in order, tracked in schema_migrations.
+
+    Migrations from day one (spec §8.1 rule 9): never hand-edit the database;
+    every schema change is a new numbered file.
+    """
+    if db_path is None:
+        # Derive the SQLite file path from the engine URL
+        db_path = engine.url.database
+        if db_path in (None, ":memory:"):
+            raise RuntimeError("run_migrations requires a file-backed SQLite database")
+
+    conn = sqlite3.connect(db_path)
+    try:
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS schema_migrations ("
+            "  version INTEGER PRIMARY KEY,"
+            "  applied_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))"
+            ")"
+        )
+        applied = {row[0] for row in conn.execute("SELECT version FROM schema_migrations")}
+
+        for path in sorted(MIGRATIONS_DIR.glob("*.sql")):
+            match = re.match(r"(\d+)", path.name)
+            if not match:
+                continue
+            version = int(match.group(1))
+            if version in applied:
+                continue
+            conn.executescript(path.read_text())
+            conn.execute("INSERT INTO schema_migrations (version) VALUES (?)", (version,))
+            conn.commit()
+    finally:
+        conn.close()