refactor: reorganize project structure and update configurations

- Move migrations/ to database/schema/ for clarity on database schema definitions
- Move sqlc.yaml to internal/database/ to group with database code
- Move static/ to cmd/server/static/ to co-locate with server
- Update all configuration files and documentation
- Follow Go project conventions for better organization

database/schema/008_add_user_names.up.sql

@@ -0,0 +1,3 @@
+-- Add first and last name to users table
+ALTER TABLE users ADD COLUMN first_name VARCHAR(255);
+ALTER TABLE users ADD COLUMN last_name VARCHAR(255);