Add Democratic fundraising platform.

Co-authored-by: Cursor <cursoragent@cursor.com>

prisma/migrations/20260515210000_user_username/migration.sql

@@ -0,0 +1,26 @@
+-- Add optional username column, backfill, then constrain.
+ALTER TABLE "User" ADD COLUMN "username" TEXT;
+
+UPDATE "User"
+SET "username" =
+  LEFT(
+    COALESCE(
+      NULLIF(
+        regexp_replace(
+          lower(trim(split_part("email", '@', 1))),
+          '[^a-z0-9_]',
+          '_',
+          'g'
+        ),
+        ''
+      ),
+      'supporter'
+    ),
+    23
+  )
+  || '_'
+  || right(replace("id", '-', ''), 8);
+
+ALTER TABLE "User" ALTER COLUMN "username" SET NOT NULL;
+
+CREATE UNIQUE INDEX "User_username_key" ON "User" ("username");