feat(backend): consolidate queue logic for scheduling

backend/database/models/_base.py

@@ -0,0 +1,49 @@
+from __future__ import annotations
+from dataclasses import dataclass, asdict, fields
+from datetime import date, datetime
+from typing import Any, Dict, Tuple, Type, TypeVar, Union
+
+Row = Tuple[Any, ...] | Dict[str, Any]   # what sqlite3.Row returns
+
+T = TypeVar("T", bound="BaseModel")
+
+
+@dataclass()
+class BaseModel:
+    """A tiny helper that gives every model a common interface."""
+
+    @classmethod
+    def from_row(cls: Type[T], row: Row) -> T:
+        """
+        Build a model instance from a sqlite3.Row (or a dict‑like object).
+        Column names are matched to the dataclass field names.
+        """
+        if isinstance(row, dict):
+            data = row
+        else:   # sqlite3.Row behaves like a mapping, but we guard for safety
+            data = dict(row)
+
+        # Convert raw strings to proper Python types where we know the annotation
+        converted: Dict[str, Any] = {}
+        for f in fields(cls):
+            value = data.get(f.name)
+            if value is None:
+                converted[f.name] = None
+                continue
+
+            # datetime/date handling – sqlite returns str in ISO format
+            if f.type is datetime:
+                converted[f.name] = datetime.fromisoformat(value)
+            elif f.type is date:
+                converted[f.name] = date.fromisoformat(value)
+            else:
+                converted[f.name] = value
+        return cls(**converted)          # type: ignore[arg-type]
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Return a plain dict (useful for INSERT/UPDATE statements)."""
+        return asdict(self)
+
+    def __repr__(self) -> str:  # a nicer representation when printing
+        field_vals = ", ".join(f"{f.name}={getattr(self, f.name)!r}" for f in fields(self))
+        return f"{self.__class__.__name__}({field_vals})"