refactor: break up large functions, add RPG/league/salary/burnout, fix bugs, add tests

- Refactor GenerateMonthlyReport (198→70), HandleCallback (128→85),
  handleHistoryCallback (131→38), handleExportCallback (100→25),
  checkAchievements (86→25) into extracted helper functions
- Add RPG system (XP, levels, streak, achievements, burnout)
- Add WorkTime League leaderboard
- Add salary estimation with configurable currency/rate
- Add input sanitization (SanitizeNote, SanitizeDisplayName)
- Add settings select-style pickers for toggles (report, RPG, league)
- Add break threshold inline picker UI
- Add event notes with pending state and /note command
- Add multi-calendar support (Jalali, Hijri)
- Add Excel export with theme picker
- Fix: getTodayBreakThreshold uses user's timezone (was UTC)
- Fix: acknowledgeCallback passes real callback ID
- Fix: currency symbol safety with currencySymbol() helper
- Fix: count work hours in summary on day-off days
- Fix: unsilence all error returns from SQL Exec/Bot API/migrations
- Remove stale db/schema.sql and unreferenced computeWeekTotals
- Extract constants: DateLayout, TimeLayout, secondsPerHour, etc.
- Add 12 new tests (XP, salary, sanitize, currency, dateutil)
- Remove duplicate package doc comment in totals.go

internal/bot/rpg_test.go

@@ -0,0 +1,173 @@
+package bot
+
+import (
+	"testing"
+)
+
+func TestXpForLevel(t *testing.T) {
+	cases := []struct {
+		n    int
+		want int64
+	}{
+		{0, 0},
+		{1, 100},
+		{2, 300},
+		{5, 1500},
+		{10, 5500},
+		{27, 37800},
+		{50, 127500},
+	}
+	for _, c := range cases {
+		got := xpForLevel(c.n)
+		if got != c.want {
+			t.Errorf("xpForLevel(%d) = %d, want %d", c.n, got, c.want)
+		}
+	}
+}
+
+func TestLevelForXP(t *testing.T) {
+	cases := []struct {
+		xp   int64
+		want int
+	}{
+		{0, 0},
+		{50, 0},
+		{99, 0},
+		{100, 1},
+		{299, 1},
+		{300, 2},
+		{5500, 10},
+		{37800, 27},
+		{127500, 50},
+	}
+	for _, c := range cases {
+		got := levelForXP(c.xp)
+		if got != c.want {
+			t.Errorf("levelForXP(%d) = %d, want %d", c.xp, got, c.want)
+		}
+	}
+}
+
+func TestLevelForXP_Monotonic(t *testing.T) {
+	for n := 0; n <= 100; n++ {
+		xp := xpForLevel(n)
+		l := levelForXP(xp)
+		if l != n {
+			t.Errorf("levelForXP(xpForLevel(%d)) = %d, want %d", n, l, n)
+		}
+	}
+}
+
+func TestXpForWorkSeconds(t *testing.T) {
+	if got := xpForWorkSeconds(0); got != 0 {
+		t.Errorf("xpForWorkSeconds(0) = %d, want 0", got)
+	}
+	if got := xpForWorkSeconds(3600); got != 3600 {
+		t.Errorf("xpForWorkSeconds(3600) = %d, want 3600", got)
+	}
+	if got := xpForWorkSeconds(1800); got != 1800 {
+		t.Errorf("xpForWorkSeconds(1800) = %d, want 1800", got)
+	}
+}
+
+func TestStreakBonus(t *testing.T) {
+	cases := []struct {
+		streak int
+		want   int64
+	}{
+		{0, 0},
+		{1, 50},
+		{10, 500},
+		{5, 250},
+		{20, 500},
+	}
+	for _, c := range cases {
+		got := streakBonus(c.streak)
+		if got != c.want {
+			t.Errorf("streakBonus(%d) = %d, want %d", c.streak, got, c.want)
+		}
+	}
+}
+
+func TestCurrencySymbol(t *testing.T) {
+	cases := []struct {
+		currency string
+		want     string
+	}{
+		{"", "$"},
+		{"$", "$"},
+		{"$ USD", "$"},
+		{"€ EUR", "€"},
+		{"£", "£"},
+		{"Toman", "Toman"},
+		{"   ", "$"},
+	}
+	for _, c := range cases {
+		got := currencySymbol(c.currency)
+		if got != c.want {
+			t.Errorf("currencySymbol(%q) = %q, want %q", c.currency, got, c.want)
+		}
+	}
+}
+
+func TestComputeDailySalary(t *testing.T) {
+	// 1 hour at $25/hr
+	got := computeDailySalary(3600, 25.0)
+	if got != 25.0 {
+		t.Errorf("computeDailySalary(3600, 25) = %.2f, want 25.00", got)
+	}
+
+	// 2.5 hours at $20/hr = $50
+	got = computeDailySalary(9000, 20.0)
+	if got != 50.0 {
+		t.Errorf("computeDailySalary(9000, 20) = %.2f, want 50.00", got)
+	}
+
+	// 0 seconds = $0
+	got = computeDailySalary(0, 50.0)
+	if got != 0 {
+		t.Errorf("computeDailySalary(0, 50) = %.2f, want 0", got)
+	}
+
+	// rounding: 3599 sec (0.9997 hr) at $10/hr = $9.997 -> $10.00
+	got = computeDailySalary(3599, 10.0)
+	if got != 10.0 {
+		t.Errorf("computeDailySalary(3599, 10) = %.2f, want 10.00", got)
+	}
+}
+
+func TestSanitizeNote(t *testing.T) {
+	// Trims spaces
+	if got := SanitizeNote("  hello  "); got != "hello" {
+		t.Errorf("SanitizeNote trim: got %q", got)
+	}
+
+	// Removes control chars except newline/tab
+	if got := SanitizeNote("he\x00llo\nworld\t!"); got != "hello\nworld\t!" {
+		t.Errorf("SanitizeNote control: got %q", got)
+	}
+
+	// Preserves newlines and tabs
+	if got := SanitizeNote("line1\nline2\tindented"); got != "line1\nline2\tindented" {
+		t.Errorf("SanitizeNote newline/tab: got %q", got)
+	}
+
+	// Truncates long notes
+	long := string(make([]byte, 600))
+	for i := range long {
+		long = long[:i] + "a" + long[i+1:]
+	}
+	got := SanitizeNote(long)
+	if len(got) > 500 {
+		t.Errorf("SanitizeNote length: got %d, want <= 500", len(got))
+	}
+}
+
+func TestSanitizeDisplayName(t *testing.T) {
+	if got := SanitizeDisplayName("  Alice  "); got != "Alice" {
+		t.Errorf("SanitizeDisplayName trim: got %q", got)
+	}
+	if got := SanitizeDisplayName("Ali\x00ce"); got != "Alice" {
+		t.Errorf("SanitizeDisplayName control: got %q", got)
+	}
+}