refactor: redesign planos interface with design system patterns

- Create CreatePlanModal component with Headless UI Dialog
- Implement dark mode support throughout plans UI
- Update plans/page.tsx with professional card layout
- Update plans/[id]/page.tsx with consistent styling
- Add proper spacing, typography, and color consistency
- Implement smooth animations and transitions
- Add success/error message feedback
- Improve form UX with better input styling

postgres/migrations/009_create_plans_table.sql

@@ -0,0 +1,25 @@
+-- Create plans table
+CREATE TABLE IF NOT EXISTS plans (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    name VARCHAR(255) NOT NULL,
+    slug VARCHAR(100) NOT NULL UNIQUE,
+    description TEXT,
+    min_users INTEGER NOT NULL DEFAULT 1,
+    max_users INTEGER NOT NULL DEFAULT 30, -- -1 means unlimited
+    monthly_price NUMERIC(10, 2),
+    annual_price NUMERIC(10, 2),
+    features TEXT[] NOT NULL DEFAULT '{}',
+    differentiators TEXT[] NOT NULL DEFAULT '{}',
+    storage_gb INTEGER NOT NULL DEFAULT 1,
+    is_active BOOLEAN NOT NULL DEFAULT true,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Add indexes
+CREATE INDEX idx_plans_slug ON plans(slug);
+CREATE INDEX idx_plans_is_active ON plans(is_active);
+
+-- Add comments
+COMMENT ON TABLE plans IS 'Subscription plans for agencies';
+COMMENT ON COLUMN plans.max_users IS '-1 means unlimited users';