fix: address audit findings — nil pointers, timezone bug, dead code, tests, README

- Fix nil pointer dereference in clock.go (guard GetOrCreateSettings and
  GetOrCreateRPGStats errors before accessing fields)
- Fix timezone bug in handleSetBreakMsg (was using system time.Now()
  instead of user's configured timezone)
- Remove dead code: sendExportMonthPicker (unused wrapper)
- Simplify xpForWorkSeconds (xpPerSecond=1, inline to just return sec)
- Extract computeStreakFromDates as pure testable function from
  recalcAggregates; add 6 tests covering empty, current, gaps,
  no-today, long streak, longest-not-current edge cases
- Update README with full feature documentation: RPG, League, Salary,
  Burnout, Work Types, Inline History Editing, all missing commands

internal/bot/rpg_test.go

@@ -1,6 +1,7 @@
 package bot
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 )
@@ -225,3 +226,72 @@ func TestComputeTrendFromAvgs(t *testing.T) {
 		}
 	}
 }
+
+func TestComputeStreakFromDates_Empty(t *testing.T) {
+	cur, longest := computeStreakFromDates(nil, "2026-06-25")
+	if cur != 0 || longest != 0 {
+		t.Errorf("empty dates: got (%d, %d), want (0, 0)", cur, longest)
+	}
+}
+
+func TestComputeStreakFromDates_CurrentOnly(t *testing.T) {
+	dates := []string{"2026-06-25", "2026-06-26"}
+	cur, longest := computeStreakFromDates(dates, "2026-06-26")
+	if cur != 2 {
+		t.Errorf("current streak = %d, want 2", cur)
+	}
+	if longest != 2 {
+		t.Errorf("longest streak = %d, want 2", longest)
+	}
+}
+
+func TestComputeStreakFromDates_GapBreaksStreak(t *testing.T) {
+	dates := []string{"2026-06-23", "2026-06-25", "2026-06-26"}
+	cur, longest := computeStreakFromDates(dates, "2026-06-26")
+	if cur != 2 {
+		t.Errorf("current streak = %d, want 2 (today and yesterday)", cur)
+	}
+	if longest != 2 {
+		t.Errorf("longest streak = %d, want 2", longest)
+	}
+}
+
+func TestComputeStreakFromDates_NoEventsToday(t *testing.T) {
+	dates := []string{"2026-06-24", "2026-06-25"}
+	cur, longest := computeStreakFromDates(dates, "2026-06-26")
+	if cur != 0 {
+		t.Errorf("current streak = %d, want 0 (no events today)", cur)
+	}
+	if longest != 2 {
+		t.Errorf("longest streak = %d, want 2", longest)
+	}
+}
+
+func TestComputeStreakFromDates_LongStreak(t *testing.T) {
+	dates := []string{}
+	for d := 1; d <= 10; d++ {
+		dates = append(dates, fmt.Sprintf("2026-06-%02d", d))
+	}
+	cur, longest := computeStreakFromDates(dates, "2026-06-10")
+	if cur != 10 {
+		t.Errorf("current streak = %d, want 10", cur)
+	}
+	if longest != 10 {
+		t.Errorf("longest streak = %d, want 10", longest)
+	}
+}
+
+func TestComputeStreakFromDates_LongestNotCurrent(t *testing.T) {
+	dates := []string{}
+	for d := 1; d <= 5; d++ {
+		dates = append(dates, fmt.Sprintf("2026-06-%02d", d))
+	}
+	dates = append(dates, "2026-06-09", "2026-06-10")
+	cur, longest := computeStreakFromDates(dates, "2026-06-10")
+	if cur != 2 {
+		t.Errorf("current streak = %d, want 2", cur)
+	}
+	if longest != 5 {
+		t.Errorf("longest streak = %d, want 5", longest)
+	}
+}