feat: implement merchant dashboard, secure auth, and short_id system

- Added dedicated merchant dashboard with analytics and transactions
- Implemented API Key based authentication for merchants
- Introduced 8-character Short IDs for merchants to use in URLs
- Refactored checkout and payment intent APIs to support multi-gateway
- Enhanced Landing Page with Merchant Portal access and marketing copy
- Fixed Next.js 15 async params build issues
- Updated internal branding to P2CGateway
- Added AyrisTech credits to footer

docs/update_schema_short_ids.sql

@@ -0,0 +1,25 @@
+-- Add short_id column to merchants
+ALTER TABLE merchants ADD COLUMN IF NOT EXISTS short_id TEXT UNIQUE;
+
+-- Function to generate a random short ID
+CREATE OR REPLACE FUNCTION generate_short_id() RETURNS TEXT AS $$
+DECLARE
+    chars TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
+    result TEXT := '';
+    i INTEGER := 0;
+BEGIN
+    FOR i IN 1..8 LOOP
+        result := result || substr(chars, floor(random() * length(chars) + 1)::integer, 1);
+    END LOOP;
+    RETURN result;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Update existing merchants with a short_id
+UPDATE merchants SET short_id = generate_short_id() WHERE short_id IS NULL;
+
+-- Make short_id required for further inserts
+-- ALTER TABLE merchants ALTER COLUMN short_id SET NOT NULL; -- Can do this after update
+
+-- Add owner_id to merchants to link with Supabase Auth users
+ALTER TABLE merchants ADD COLUMN IF NOT EXISTS owner_id UUID REFERENCES auth.users(id);