feat(savings): Add savings module with categories, transactions, recurring plans

- Categories: regular, deposits, credits, recurring, multi-user, accounts
- Transactions: deposits and withdrawals with user tracking
- Recurring plans: monthly payment obligations per user
- Stats: overdues calculation with allocation algorithm
- Excludes is_account categories from total sums
- Documentation: docs/SAVINGS.md

internal/repository/db.go

@@ -95,6 +95,28 @@ func RunMigrations(db *sqlx.DB) error {
 		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS reminder_time TIME`,
 		`ALTER TABLE habits ADD COLUMN IF NOT EXISTS reminder_time TIME`,
 		`CREATE INDEX IF NOT EXISTS idx_users_telegram_chat_id ON users(telegram_chat_id)`,
+		// Recurring tasks support
+		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS is_recurring BOOLEAN DEFAULT false`,
+		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS recurrence_type VARCHAR(20)`,
+		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS recurrence_interval INTEGER DEFAULT 1`,
+		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS recurrence_end_date DATE`,
+		`ALTER TABLE tasks ADD COLUMN IF NOT EXISTS parent_task_id INTEGER REFERENCES tasks(id) ON DELETE SET NULL`,
+		`CREATE INDEX IF NOT EXISTS idx_tasks_parent_id ON tasks(parent_task_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tasks_recurring ON tasks(is_recurring) WHERE is_recurring = true`,
+		// Habit freezes support
+		`CREATE TABLE IF NOT EXISTS habit_freezes (
+			id SERIAL PRIMARY KEY,
+			habit_id INTEGER REFERENCES habits(id) ON DELETE CASCADE,
+			user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
+			start_date DATE NOT NULL,
+			end_date DATE NOT NULL,
+			reason VARCHAR(255) DEFAULT '',
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		)`,
+		`CREATE INDEX IF NOT EXISTS idx_habit_freezes_habit ON habit_freezes(habit_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_habit_freezes_dates ON habit_freezes(start_date, end_date)`,
+		// Habit start_date support
+		`ALTER TABLE habits ADD COLUMN IF NOT EXISTS start_date DATE`,
 	}
 
 	for _, migration := range migrations {