refactor: Migrate to API v2

- Added auto schema migration
- Refactored /api/subs, /api/collections, /api/artifacts. Now these APIs will return array instead of object. This enables sorting items in the future.

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "sub-store",
-  "version": "2.3.2",
+  "version": "2.4.0",
   "description": "Advanced Subscription Manager for QX, Loon, Surge, Stash and ShadowRocket.",
   "main": "src/main.js",
   "scripts": {
@@ -18,6 +18,7 @@
     "js-base64": "^3.7.2",
     "lodash": "^4.17.21",
     "request": "^2.88.2",
+    "semver": "^7.3.7",
     "static-js-yaml": "^1.0.0"
   },
   "devDependencies": {