adding migration files to lower index username and email

prisma/migrations/20260324100000_add_ci_username_unique_index/migration.sql

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+-- Add case-insensitive unique indexes to prevent TOCTOU race conditions
+-- These ensure the database enforces uniqueness regardless of casing
+CREATE UNIQUE INDEX "users_username_ci_unique" ON "users" (LOWER("username"));
+CREATE UNIQUE INDEX "users_email_ci_unique" ON "users" (LOWER("email"));