feat(notifications): add full notification system (DB migration, hooks, UI, generators)

- Add DB migration script to create notifications and notification_preferences tables with RLS, indexes, triggers and cleanup function
- Implement React Query hooks: fetch notifications, unread count, mark as read, mark all read, delete, fetch/update preferences
- Add notification generation utilities: createNotification, checkBudgetAlerts, checkSavingsGoalMilestones, generateSpendingInsights, generateDailyTip
- Add UI components: NotificationPanel, NotificationItem, ScrollArea (Radix wrapper) and integrate panel into TopBar
- Add developer docs: implementation guide and status summary
- Install @radix-ui/react-scroll-area and bump package version to 1.0.0

Author: Motakabbir

docs/database/migration_add_notifications.sql

@@ -0,0 +1,134 @@
+-- Add notifications table
+CREATE TABLE IF NOT EXISTS notifications (
+    id UUID PRIMARY KEY DEFAULT uuid_generate_v4 (),
+    user_id UUID NOT NULL REFERENCES auth.users (id) ON DELETE CASCADE,
+    type VARCHAR(50) NOT NULL,
+    title VARCHAR(255) NOT NULL,
+    message TEXT NOT NULL,
+    icon VARCHAR(50),
+    priority VARCHAR(20) DEFAULT 'normal' CHECK (
+        priority IN (
+            'low',
+            'normal',
+            'high',
+            'urgent'
+        )
+    ),
+    is_read BOOLEAN DEFAULT false,
+    action_url VARCHAR(255),
+    metadata JSONB,
+    created_at TIMESTAMP
+    WITH
+        TIME ZONE DEFAULT NOW(),
+        read_at TIMESTAMP
+    WITH
+        TIME ZONE,
+        expires_at TIMESTAMP
+    WITH
+        TIME ZONE
+);
+
+-- Add indexes for better performance
+CREATE INDEX IF NOT EXISTS idx_notifications_user_read ON notifications (user_id, is_read);
+
+CREATE INDEX IF NOT EXISTS idx_notifications_created ON notifications (created_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_notifications_type ON notifications(type);
+
+-- Row Level Security for notifications
+ALTER TABLE notifications ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS "Users can view own notifications" ON notifications;
+
+CREATE POLICY "Users can view own notifications" ON notifications FOR
+SELECT USING (auth.uid () = user_id);
+
+DROP POLICY IF EXISTS "Users can insert own notifications" ON notifications;
+
+CREATE POLICY "Users can insert own notifications" ON notifications FOR
+INSERT
+WITH
+    CHECK (auth.uid () = user_id);
+
+DROP POLICY IF EXISTS "Users can update own notifications" ON notifications;
+
+CREATE POLICY "Users can update own notifications" ON notifications FOR
+UPDATE USING (auth.uid () = user_id);
+
+DROP POLICY IF EXISTS "Users can delete own notifications" ON notifications;
+
+CREATE POLICY "Users can delete own notifications" ON notifications FOR DELETE USING (auth.uid () = user_id);
+
+-- Add notification_preferences table
+CREATE TABLE IF NOT EXISTS notification_preferences (
+    id UUID PRIMARY KEY DEFAULT uuid_generate_v4 (),
+    user_id UUID NOT NULL UNIQUE REFERENCES auth.users (id) ON DELETE CASCADE,
+    budget_alerts BOOLEAN DEFAULT true,
+    goal_milestones BOOLEAN DEFAULT true,
+    spending_insights BOOLEAN DEFAULT true,
+    daily_tips BOOLEAN DEFAULT false,
+    weekly_summary BOOLEAN DEFAULT true,
+    created_at TIMESTAMP
+    WITH
+        TIME ZONE DEFAULT NOW(),
+        updated_at TIMESTAMP
+    WITH
+        TIME ZONE DEFAULT NOW()
+);
+
+-- Row Level Security for notification_preferences
+ALTER TABLE notification_preferences ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS "Users can view own preferences" ON notification_preferences;
+
+CREATE POLICY "Users can view own preferences" ON notification_preferences FOR
+SELECT USING (auth.uid () = user_id);
+
+DROP POLICY IF EXISTS "Users can insert own preferences" ON notification_preferences;
+
+CREATE POLICY "Users can insert own preferences" ON notification_preferences FOR
+INSERT
+WITH
+    CHECK (auth.uid () = user_id);
+
+DROP POLICY IF EXISTS "Users can update own preferences" ON notification_preferences;
+
+CREATE POLICY "Users can update own preferences" ON notification_preferences FOR
+UPDATE USING (auth.uid () = user_id);
+
+-- Function to create default notification preferences for new users
+CREATE OR REPLACE FUNCTION create_default_notification_preferences()
+RETURNS TRIGGER AS $$
+BEGIN
+  INSERT INTO notification_preferences (user_id)
+  VALUES (NEW.id)
+  ON CONFLICT (user_id) DO NOTHING;
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql SECURITY DEFINER;
+
+-- Trigger to automatically create notification preferences for new users
+DROP TRIGGER IF EXISTS on_auth_user_created_notification_prefs ON auth.users;
+
+CREATE TRIGGER on_auth_user_created_notification_prefs
+  AFTER INSERT ON auth.users
+  FOR EACH ROW
+  EXECUTE FUNCTION create_default_notification_preferences();
+
+-- Function to clean up expired notifications
+CREATE OR REPLACE FUNCTION cleanup_expired_notifications()
+RETURNS void AS $$
+BEGIN
+  DELETE FROM notifications
+  WHERE expires_at IS NOT NULL
+  AND expires_at < NOW();
+END;
+$$ LANGUAGE plpgsql SECURITY DEFINER;
+
+-- Optional: Create a scheduled job to clean up expired notifications
+-- This requires pg_cron extension (comment out if not available)
+-- SELECT cron.schedule(
+--   'cleanup-expired-notifications',
+--   '0 0 * * *', -- Run daily at midnight
+--   $$SELECT cleanup_expired_notifications()$$
+-- );