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/utils/dates.py

@@ -0,0 +1,41 @@
+"""Date and ISO helpers for duty ranges and API validation."""
+
+import re
+from datetime import date, datetime, timezone
+
+
+def day_start_iso(d: date) -> str:
+    """ISO 8601 start of calendar day UTC: YYYY-MM-DDT00:00:00Z."""
+    return d.isoformat() + "T00:00:00Z"
+
+
+def day_end_iso(d: date) -> str:
+    """ISO 8601 end of calendar day UTC: YYYY-MM-DDT23:59:59Z."""
+    return d.isoformat() + "T23:59:59Z"
+
+
+def duty_to_iso(d: date, hour_utc: int, minute_utc: int) -> str:
+    """ISO 8601 with Z for start of duty on date d at given UTC time."""
+    dt = datetime(d.year, d.month, d.day, hour_utc, minute_utc, 0, tzinfo=timezone.utc)
+    return dt.strftime("%Y-%m-%dT%H:%M:%SZ")
+
+
+_ISO_DATE_RE = re.compile(r"^\d{4}-\d{2}-\d{2}$")
+
+
+def parse_iso_date(s: str) -> date | None:
+    """Parse YYYY-MM-DD string to date. Returns None if invalid."""
+    if not s or not _ISO_DATE_RE.match(s.strip()):
+        return None
+    try:
+        return date.fromisoformat(s.strip())
+    except ValueError:
+        return None
+
+
+def validate_date_range(from_date: str, to_date: str) -> None:
+    """Validate from_date and to_date are YYYY-MM-DD and from_date <= to_date. Raises ValueError if invalid."""
+    if not _ISO_DATE_RE.match(from_date or "") or not _ISO_DATE_RE.match(to_date or ""):
+        raise ValueError("Параметры from и to должны быть в формате YYYY-MM-DD")
+    if from_date > to_date:
+        raise ValueError("Дата from не должна быть позже to")