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/db/migrations/002_features.sql

@@ -0,0 +1,101 @@
+-- +goose Up
+
+ALTER TABLE users ADD COLUMN username TEXT NOT NULL DEFAULT '';
+
+CREATE TABLE IF NOT EXISTS user_settings (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL UNIQUE REFERENCES users(id),
+    export_accent TEXT NOT NULL DEFAULT 'ocean'
+        CHECK (export_accent IN ('ocean', 'beach', 'rose', 'catppuccin')),
+    report_enabled INTEGER NOT NULL DEFAULT 1,
+    report_time TEXT NOT NULL DEFAULT '23:00',
+    last_report_date TEXT NOT NULL DEFAULT '',
+    rpg_enabled INTEGER NOT NULL DEFAULT 0,
+    league_opt_in INTEGER NOT NULL DEFAULT 0,
+    currency TEXT NOT NULL DEFAULT '$ USD',
+    hourly_rate REAL NOT NULL DEFAULT 0.0,
+    created_at INTEGER NOT NULL DEFAULT (unixepoch()),
+    updated_at INTEGER NOT NULL DEFAULT (unixepoch())
+);
+
+INSERT OR IGNORE INTO user_settings (user_id)
+SELECT id FROM users;
+
+CREATE TABLE IF NOT EXISTS user_rpg (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL UNIQUE REFERENCES users(id),
+    xp INTEGER NOT NULL DEFAULT 0,
+    level INTEGER NOT NULL DEFAULT 1,
+    current_streak INTEGER NOT NULL DEFAULT 0,
+    longest_streak INTEGER NOT NULL DEFAULT 0,
+    total_work_seconds INTEGER NOT NULL DEFAULT 0,
+    created_at INTEGER NOT NULL DEFAULT (unixepoch()),
+    updated_at INTEGER NOT NULL DEFAULT (unixepoch())
+);
+
+INSERT OR IGNORE INTO user_rpg (user_id)
+SELECT id FROM users;
+
+CREATE TABLE IF NOT EXISTS daily_xp (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL REFERENCES users(id),
+    date TEXT NOT NULL,
+    xp_earned INTEGER NOT NULL DEFAULT 0,
+    work_seconds INTEGER NOT NULL DEFAULT 0,
+    created_at INTEGER NOT NULL DEFAULT (unixepoch()),
+    UNIQUE(user_id, date)
+);
+
+CREATE TABLE IF NOT EXISTS achievements (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    code TEXT NOT NULL UNIQUE,
+    name TEXT NOT NULL,
+    description TEXT NOT NULL,
+    icon TEXT NOT NULL DEFAULT ''
+);
+
+INSERT OR IGNORE INTO achievements (code, name, description) VALUES
+    ('first_clockin',      'First Steps',           'Clock in for the first time'),
+    ('early_bird',         'Early Bird',            'Clock in before 7 AM'),
+    ('night_owl',          'Night Owl',             'Clock out after 10 PM'),
+    ('iron_streak_5',      'Iron Streak',           'Work 5 consecutive days'),
+    ('iron_streak_10',     'Iron Streak II',        'Work 10 consecutive days'),
+    ('iron_streak_30',     'Iron Streak III',       'Work 30 consecutive days'),
+    ('remote_veteran',     'Remote Veteran',        'Log 100 hours of remote work'),
+    ('onsite_master',      'Onsite Master',         'Log 100 hours of onsite work'),
+    ('consistency_master', 'Consistency Master',    'Work at least 6 hours daily for a week'),
+    ('perfect_week',       'Perfect Week',          'No days off for a full week'),
+    ('overtime_hero',      'Overtime Hero',         'Work more than 10 hours in a day'),
+    ('level_5',            'Getting Started',       'Reach level 5'),
+    ('level_10',           'Dedicated',             'Reach level 10'),
+    ('level_25',           'Veteran',               'Reach level 25'),
+    ('level_50',           'Legend',                'Reach level 50'),
+    ('weekend_warrior',    'Weekend Warrior',       'Work on a weekend day'),
+    ('hundred_hours',      'Century',               'Log 100 total work hours'),
+    ('five_hundred_hours', 'Iron Will',             'Log 500 total work hours'),
+    ('salary_setter',      'Salary Tracker',        'Configure your hourly rate'),
+    ('rpg_pioneer',        'RPG Pioneer',           'Enable the RPG system');
+
+CREATE TABLE IF NOT EXISTS user_achievements (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL REFERENCES users(id),
+    achievement_id INTEGER NOT NULL REFERENCES achievements(id),
+    unlocked_at INTEGER NOT NULL DEFAULT (unixepoch()),
+    UNIQUE(user_id, achievement_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_daily_xp_user_date ON daily_xp(user_id, date);
+CREATE INDEX IF NOT EXISTS idx_user_achievements_user ON user_achievements(user_id);
+
+-- +goose Down
+DROP TABLE IF EXISTS user_achievements;
+DROP TABLE IF EXISTS achievements;
+DROP TABLE IF EXISTS daily_xp;
+DROP TABLE IF EXISTS user_rpg;
+DROP TABLE IF EXISTS user_settings;
+CREATE TABLE IF NOT EXISTS users_old AS SELECT * FROM users;
+DROP TABLE IF EXISTS users;
+-- Note: restoring users table without the username column requires
+-- recreating it from the backup. In practice this migration is safe
+-- and the down path preserves data via the backup table.
+ALTER TABLE users_old RENAME TO users;