feat: migrate to Cloudflare Workers with icon and version upload

Replace Express/SQLite and web/ with frontend/, worker/, and wrangler deploy. Add optional app icon upload, date-based app_version, and build-app workflow input.

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

worker/migrations/0001_init.sql

@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS builds (
+  id TEXT PRIMARY KEY,
+  app_name TEXT NOT NULL,
+  app_name_en TEXT NOT NULL DEFAULT '',
+  app_identifier TEXT NOT NULL,
+  status TEXT NOT NULL DEFAULT 'pending',
+  workflow_run_id INTEGER,
+  windows_url TEXT,
+  android_url TEXT,
+  error TEXT,
+  created_at TEXT NOT NULL DEFAULT (datetime('now')),
+  updated_at TEXT NOT NULL DEFAULT (datetime('now'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_builds_created_at ON builds(created_at DESC);