feat: implement annual subscription model across backend quota system and flutter UI

update_annual_plans.sql

@@ -0,0 +1,46 @@
+-- 1. Update existing plans to annual quotas and pricing
+-- We'll assume the basic plan ID is 'basic' and pro is 'pro'. If they are different, they will need adjusting.
+
+-- Basic Plan (Annual)
+UPDATE subscription_plans 
+SET 
+    name_ar = 'الباقة الأساسية (سنوي)', 
+    name_en = 'Basic Plan (Annual)',
+    price = 120.00,
+    max_invoices_per_month = 12000,
+    max_companies = 1,
+    max_users = 1
+WHERE id = 'basic';
+
+-- Pro Plan (Annual)
+UPDATE subscription_plans 
+SET 
+    name_ar = 'الباقة الاحترافية (سنوي)', 
+    name_en = 'Pro Plan (Annual)',
+    price = 250.00,
+    max_invoices_per_month = 50000,
+    max_companies = 9999, -- unlimited
+    max_users = 5
+WHERE id = 'pro';
+
+-- Free Trial Plan
+UPDATE subscription_plans 
+SET 
+    name_ar = 'التجربة المجانية', 
+    name_en = 'Free Trial',
+    price = 0.00,
+    max_invoices_per_month = 15,
+    max_companies = 1,
+    max_users = 1
+WHERE id = 'free';
+
+-- 2. Update existing active subscriptions to match the new annual quota limits so no one gets blocked
+UPDATE subscriptions s
+JOIN subscription_plans sp ON s.plan_id = sp.id
+SET 
+    s.max_invoices_per_month = sp.max_invoices_per_month,
+    s.max_companies = sp.max_companies,
+    s.max_users = sp.max_users,
+    -- Adjust the period end to +1 year if it's currently set to a month (for paid plans only)
+    s.current_period_end = IF(s.plan_id != 'free', DATE_ADD(s.current_period_start, INTERVAL 1 YEAR), s.current_period_end);
+