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/.vite/deps/_metadata.json

@@ -0,0 +1,61 @@
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+  "configHash": "8650f1e7",
+  "lockfileHash": "5c581817",
+  "browserHash": "3c2245d4",
+  "optimized": {
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+      "file": "react.js",
+      "fileHash": "15c97ccd",
+      "needsInterop": true
+    },
+    "react-dom": {
+      "src": "../../react-dom/index.js",
+      "file": "react-dom.js",
+      "fileHash": "86a95bc2",
+      "needsInterop": true
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+      "needsInterop": true
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+    "react/jsx-runtime": {
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+      "file": "react_jsx-runtime.js",
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+      "needsInterop": true
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+    "date-fns": {
+      "src": "../../date-fns/index.js",
+      "file": "date-fns.js",
+      "fileHash": "ca52e344",
+      "needsInterop": false
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+    "react-dom/client": {
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+      "file": "react-dom_client.js",
+      "fileHash": "85c858ea",
+      "needsInterop": true
+    },
+    "react-router-dom": {
+      "src": "../../react-router-dom/dist/index.mjs",
+      "file": "react-router-dom.js",
+      "fileHash": "c2f3a9fa",
+      "needsInterop": false
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+  "chunks": {
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+      "file": "chunk-UK5KQJRU.js"
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+}