add blocker presets

backend/app/services/pomodoro.py

@@ -216,6 +216,25 @@ def extend(session: Session, minutes: int) -> PomodoroSession:
     return row
 
 
+def rescale_current(session: Session, settings: AppSettings) -> PomodoroSession | None:
+    """Resize the running/paused interval to match a just-saved duration.
+
+    Without this, a preset (or any Focus/Short/Long edit) only takes effect
+    from the *next* interval — the one already ticking keeps whatever length
+    it was born with. `elapsed_seconds` is wall-clock, not stored, so this
+    only has to move `planned_seconds`; time already spent still counts, it
+    is just measured against the new total.
+    """
+    row = current_session(session)
+    if row is None:
+        return None
+    planned = duration_for(settings, row.kind)  # type: ignore[arg-type]
+    if planned != row.planned_seconds:
+        row.planned_seconds = planned
+        session.commit()
+    return row
+
+
 def attach_task(session: Session, task_id: int | None) -> PomodoroSession:
     row = _require_active(session)
     if task_id is None: