Add admin account with user management endpoints

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/main.py

@@ -2,14 +2,37 @@ from contextlib import asynccontextmanager
 
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
+from sqlalchemy import select
 
-from app.database import init_db
-from app.routers import auth, users, entries, public
+from app.config import settings
+from app.database import init_db, AsyncSessionLocal
+from app.routers import auth, users, entries, public, admin
+
+
+async def _seed_admin() -> None:
+    from app.models.user import User
+    from app.utils.security import hash_password
+
+    async with AsyncSessionLocal() as db:
+        result = await db.execute(select(User).where(User.email == settings.admin_username))
+        user = result.scalar_one_or_none()
+        if user is None:
+            db.add(User(
+                email=settings.admin_username,
+                password_hash=hash_password(settings.admin_password),
+                display_name="Admin",
+                is_admin=True,
+            ))
+        else:
+            user.password_hash = hash_password(settings.admin_password)
+            user.is_admin = True
+        await db.commit()
 
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     await init_db()
+    await _seed_admin()
     yield
 
 
@@ -26,3 +49,4 @@ app.include_router(auth.router)
 app.include_router(users.router)
 app.include_router(entries.router)
 app.include_router(public.router)
+app.include_router(admin.router)