Refactor project structure and enhance Docker configuration

- Updated `.dockerignore` to exclude test and development artifacts, optimizing the Docker image size.
- Refactored `main.py` to delegate execution to `duty_teller.run.main()`, simplifying the entry point.
- Introduced a new `duty_teller` package to encapsulate core functionality, improving modularity and organization.
- Enhanced `pyproject.toml` to define a script for running the application, streamlining the execution process.
- Updated README documentation to reflect changes in project structure and usage instructions.
- Improved Alembic environment configuration to utilize the new package structure for database migrations.

duty_teller/api/app.py

@@ -0,0 +1,62 @@
+"""FastAPI app: /api/duties and static webapp."""
+
+import logging
+
+import duty_teller.config as config
+from fastapi import Depends, FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
+from sqlalchemy.orm import Session
+
+from duty_teller.api.calendar_ics import get_calendar_events
+from duty_teller.api.dependencies import (
+    fetch_duties_response,
+    get_db_session,
+    get_validated_dates,
+    require_miniapp_username,
+)
+from duty_teller.db.schemas import CalendarEvent, DutyWithUser
+
+log = logging.getLogger(__name__)
+
+app = FastAPI(title="Duty Teller API")
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=config.CORS_ORIGINS,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/api/duties", response_model=list[DutyWithUser])
+def list_duties(
+    request: Request,
+    dates: tuple[str, str] = Depends(get_validated_dates),
+    _username: str = Depends(require_miniapp_username),
+    session: Session = Depends(get_db_session),
+):
+    from_date_val, to_date_val = dates
+    log.info(
+        "GET /api/duties from %s",
+        request.client.host if request.client else "?",
+    )
+    return fetch_duties_response(session, from_date_val, to_date_val)
+
+
+@app.get("/api/calendar-events", response_model=list[CalendarEvent])
+def list_calendar_events(
+    dates: tuple[str, str] = Depends(get_validated_dates),
+    _username: str = Depends(require_miniapp_username),
+):
+    from_date_val, to_date_val = dates
+    url = config.EXTERNAL_CALENDAR_ICS_URL
+    if not url:
+        return []
+    events = get_calendar_events(url, from_date=from_date_val, to_date=to_date_val)
+    return [CalendarEvent(date=e["date"], summary=e["summary"]) for e in events]
+
+
+webapp_path = config.PROJECT_ROOT / "webapp"
+if webapp_path.is_dir():
+    app.mount("/app", StaticFiles(directory=str(webapp_path), html=True), name="webapp")