feat: add /setcalendar command, store tests, and improve error handling

- Add /setcalendar command for calendar type parity (Settings UI)
- Add 17 store tests covering all repository methods
- Add handler tests for formatDuration, fmtHHMM, fmtDDHHMM
- Add domain tests for BurnoutLevel.String, NavMonth, FormatSalary
- Fix silent error discarding in save* helpers (log write failures)
- Fix computeAndAwardXP error handling instead of discarding
- Wrap critical store.go SQL errors with fmt.Errorf context
- Update README commands table with /setcalendar

internal/domain/rpg_test.go

@@ -157,6 +157,70 @@ func TestSanitizeNote(t *testing.T) {
 	}
 }
 
+func TestBurnoutLevelString(t *testing.T) {
+	cases := []struct {
+		level BurnoutLevel
+		want  string
+	}{
+		{BurnoutHealthy, "Healthy"},
+		{BurnoutMild, "Mild concern"},
+		{BurnoutModerate, "Moderate concern"},
+		{BurnoutHigh, "High concern"},
+		{BurnoutLevel(99), "Unknown"},
+	}
+	for _, c := range cases {
+		got := c.level.String()
+		if got != c.want {
+			t.Errorf("BurnoutLevel(%d).String() = %q, want %q", c.level, got, c.want)
+		}
+	}
+}
+
+func TestNavMonth(t *testing.T) {
+	tests := []struct {
+		y, m         int
+		prevY, prevM int
+		nextY, nextM int
+	}{
+		{2026, 6, 2026, 5, 2026, 7},
+		{2026, 1, 2025, 12, 2026, 2},
+		{2026, 12, 2026, 11, 2027, 1},
+		{2024, 2, 2024, 1, 2024, 3},
+	}
+	for _, tc := range tests {
+		prevY, prevM, nextY, nextM := NavMonth(tc.y, tc.m)
+		if prevY != tc.prevY || prevM != tc.prevM {
+			t.Errorf("NavMonth(%d, %d) prev = (%d, %d), want (%d, %d)", tc.y, tc.m, prevY, prevM, tc.prevY, tc.prevM)
+		}
+		if nextY != tc.nextY || nextM != tc.nextM {
+			t.Errorf("NavMonth(%d, %d) next = (%d, %d), want (%d, %d)", tc.y, tc.m, nextY, nextM, tc.nextY, tc.nextM)
+		}
+	}
+}
+
+func TestFormatSalary(t *testing.T) {
+	tests := []struct {
+		est       SalaryEstimate
+		currency  string
+		want      string
+		wantShort string
+	}{
+		{SalaryEstimate{GrossEarning: 1000.50}, "$ USD", "$1000.50 USD", "$1000.50"},
+		{SalaryEstimate{GrossEarning: 0}, "$ USD", "$0.00 USD", "$0.00"},
+		{SalaryEstimate{GrossEarning: 2500}, "T Toman", "T2500.00 Toman", "T2500.00"},
+	}
+	for _, tc := range tests {
+		got := tc.est.FormatSalary(tc.currency)
+		if got != tc.want {
+			t.Errorf("FormatSalary(%q) = %q, want %q", tc.currency, got, tc.want)
+		}
+		gotShort := tc.est.FormatSalaryShort(tc.currency)
+		if gotShort != tc.wantShort {
+			t.Errorf("FormatSalaryShort(%q) = %q, want %q", tc.currency, gotShort, tc.wantShort)
+		}
+	}
+}
+
 func TestSanitizeDisplayName(t *testing.T) {
 	if got := SanitizeDisplayName("  Alice  "); got != "Alice" {
 		t.Errorf("SanitizeDisplayName trim: got %q", got)