feat(03-01): create project service module

- list_projects() returns all projects ordered by created_at desc
- create_project() creates project with default models
- get_project() retrieves project by ID

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/moai/core/services/__init__.py

@@ -0,0 +1,9 @@
+"""Service layer for MoAI business logic.
+
+Services encapsulate database operations and business rules,
+providing a clean interface for handlers to use.
+"""
+
+from moai.core.services.project import create_project, get_project, list_projects
+
+__all__ = ["create_project", "get_project", "list_projects"]

src/moai/core/services/project.py

@@ -0,0 +1,57 @@
+"""Project service for MoAI.
+
+Provides CRUD operations for projects.
+"""
+
+from sqlalchemy import select
+
+from moai.core.database import get_session
+from moai.core.models import Project
+
+DEFAULT_MODELS = ["claude", "gpt", "gemini"]
+
+
+async def list_projects() -> list[Project]:
+    """List all projects ordered by creation date (newest first).
+
+    Returns:
+        List of Project objects.
+    """
+    async with get_session() as session:
+        result = await session.execute(select(Project).order_by(Project.created_at.desc()))
+        return list(result.scalars().all())
+
+
+async def create_project(name: str, models: list[str] | None = None) -> Project:
+    """Create a new project.
+
+    Args:
+        name: Human-readable project name.
+        models: List of AI model identifiers. Defaults to ["claude", "gpt", "gemini"].
+
+    Returns:
+        The created Project object.
+    """
+    if models is None:
+        models = DEFAULT_MODELS.copy()
+
+    async with get_session() as session:
+        project = Project(name=name, models=models)
+        session.add(project)
+        await session.flush()
+        await session.refresh(project)
+        return project
+
+
+async def get_project(project_id: str) -> Project | None:
+    """Get a project by ID.
+
+    Args:
+        project_id: The project's UUID.
+
+    Returns:
+        The Project object if found, None otherwise.
+    """
+    async with get_session() as session:
+        result = await session.execute(select(Project).where(Project.id == project_id))
+        return result.scalar_one_or_none()