feat: --commit flag (#44)

- --commit: после генерации отчёта сохраняет период в
  period.last_used.from/to YAML-конфига
- При period.dynamic=true следующий запуск вычисляет период от last_used:
  полный месяц → следующий месяц, произвольный диапазон → та же длина
- При period.dynamic=false перезаписывает default_from/default_to
- При period.precision=datetime сохраняет timestamps с точностью до секунд
- --commit без --output сохраняет отчёт по шаблону из конфига
- compute_next_period() в config.py
- save_period_to_config() в yaml_config.py
- 23 новых теста (7 CLI, 6 config, 6 yaml, 4 date_range)

Closes #44

redmine_reporter/config.py

@@ -350,10 +350,22 @@ class Config:
         if from_env and to_env:
             return f"{from_env}--{to_env}"
 
+        if (
+            cls._app
+            and cls._app.period_dynamic
+            and cls._app.period_last_used_from
+            and cls._app.period_last_used_to
+        ):
+            nf, nt = compute_next_period(
+                cls._app.period_last_used_from,
+                cls._app.period_last_used_to,
+                cls._app.period_precision or "date",
+            )
+            return f"{nf}--{nt}"
+
         if cls._app and cls._app.period_default_from and cls._app.period_default_to:
             return f"{cls._app.period_default_from}--{cls._app.period_default_to}"
 
-        # fallback: текущий месяц
         today = date.today()
         start = today.replace(day=1)
         if today.month == 12:
@@ -373,3 +385,50 @@ class Config:
             raise ValueError(
                 "REDMINE_API_KEY is required, or set both REDMINE_USER and REDMINE_PASSWORD"
             )
+
+
+def compute_next_period(last_from: str, last_to: str, precision: str) -> tuple[str, str]:
+    """Compute the next report period based on the last committed period.
+
+    - For a full calendar month → next full calendar month.
+    - For an arbitrary range → same duration, starting the day after last_to.
+    - For datetime precision → same duration, starting 1 second after last_to.
+    """
+    from datetime import datetime as dt_mod
+
+    if precision == "datetime":
+        fmt = "%Y-%m-%dT%H:%M:%S"
+        from_dt = dt_mod.fromisoformat(last_from.replace("Z", "+00:00"))
+        to_dt = dt_mod.fromisoformat(last_to.replace("Z", "+00:00"))
+        duration = to_dt - from_dt
+        next_from_dt = to_dt + timedelta(seconds=1)
+        next_to_dt = next_from_dt + duration
+        return next_from_dt.strftime(fmt), next_to_dt.strftime(fmt)
+
+    from_parts = last_from.split("-")
+    to_parts = last_to.split("-")
+    from_d = date(int(from_parts[0]), int(from_parts[1]), int(from_parts[2]))
+    to_d = date(int(to_parts[0]), int(to_parts[1]), int(to_parts[2]))
+
+    first_of_month = from_d.replace(day=1)
+    if from_d == first_of_month:
+        if to_d.month == 12:
+            last_of_month = date(to_d.year, 12, 31)
+        else:
+            next_first = date(to_d.year, to_d.month + 1, 1)
+            last_of_month = next_first - timedelta(days=1)
+        if to_d == last_of_month:
+            if to_d.month == 12:
+                nstart = date(to_d.year + 1, 1, 1)
+            else:
+                nstart = date(to_d.year, to_d.month + 1, 1)
+            if nstart.month == 12:
+                nend = date(nstart.year, 12, 31)
+            else:
+                nend = date(nstart.year, nstart.month + 1, 1) - timedelta(days=1)
+            return nstart.isoformat(), nend.isoformat()
+
+    duration = to_d - from_d
+    next_from = to_d + timedelta(days=1)
+    next_to = next_from + duration
+    return next_from.isoformat(), next_to.isoformat()