feat: track total berries earned in session and savegames (#61)

tests/session.rs

@@ -39,6 +39,7 @@ fn test_session_tracker_focus_to_long_break() {
     let timer_settings = TimerSettings::default();
     let mut session_tracker = SessionTracker {
         completed_focus_phases: timer_settings.long_break_interval - 1,
+        total_berries_earned: 0,
     }; // To trigger long break on next phase
 
     next_phase(&mut current_phase, &mut session_tracker, &timer_settings);
@@ -66,6 +67,7 @@ fn test_session_tracker_break_to_focus() {
     });
     let mut session_tracker = SessionTracker {
         completed_focus_phases: 1,
+        total_berries_earned: 0,
     }; // Arbitrary value, should not change
     let timer_settings = TimerSettings::default();
 
@@ -91,6 +93,7 @@ fn test_session_tracker_not_finished_phase_no_change() {
     let mut current_phase = CurrentPhase(Phase::Focus { duration: 100.0 });
     let mut session_tracker = SessionTracker {
         completed_focus_phases: 0,
+        total_berries_earned: 0,
     };
     let timer_settings = TimerSettings::default();