Add OpenAPI docs, frontend, migrations, and API updates

- OpenAPI: add missing endpoints (add-from-url, subscriptions, public availability)
- OpenAPI: CalendarSubscription schema, Subscriptions tag
- Frontend app
- Migrations: count_for_availability, subscriptions_sync, user_preferences, calendar_settings
- Config, rate limit, auth, calendar, booking, ICS, availability, user service updates

Made-with: Cursor

frontend/node_modules/caniuse-lite/package.json

@@ -0,0 +1,34 @@
+{
+  "name": "caniuse-lite",
+  "version": "1.0.30001775",
+  "description": "A smaller version of caniuse-db, with only the essentials!",
+  "main": "dist/unpacker/index.js",
+  "files": [
+    "data",
+    "dist"
+  ],
+  "keywords": [
+    "support"
+  ],
+  "author": {
+    "name": "Ben Briggs",
+    "email": "beneb.info@gmail.com",
+    "url": "http://beneb.info"
+  },
+  "repository": "browserslist/caniuse-lite",
+  "funding": [
+    {
+      "type": "opencollective",
+      "url": "https://opencollective.com/browserslist"
+    },
+    {
+      "type": "tidelift",
+      "url": "https://tidelift.com/funding/github/npm/caniuse-lite"
+    },
+    {
+      "type": "github",
+      "url": "https://github.com/sponsors/ai"
+    }
+  ],
+  "license": "CC-BY-4.0"
+}