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/json5/lib/util.js

@@ -0,0 +1,35 @@
+const unicode = require('../lib/unicode')
+
+module.exports = {
+    isSpaceSeparator (c) {
+        return typeof c === 'string' && unicode.Space_Separator.test(c)
+    },
+
+    isIdStartChar (c) {
+        return typeof c === 'string' && (
+            (c >= 'a' && c <= 'z') ||
+        (c >= 'A' && c <= 'Z') ||
+        (c === '$') || (c === '_') ||
+        unicode.ID_Start.test(c)
+        )
+    },
+
+    isIdContinueChar (c) {
+        return typeof c === 'string' && (
+            (c >= 'a' && c <= 'z') ||
+        (c >= 'A' && c <= 'Z') ||
+        (c >= '0' && c <= '9') ||
+        (c === '$') || (c === '_') ||
+        (c === '\u200C') || (c === '\u200D') ||
+        unicode.ID_Continue.test(c)
+        )
+    },
+
+    isDigit (c) {
+        return typeof c === 'string' && /[0-9]/.test(c)
+    },
+
+    isHexDigit (c) {
+        return typeof c === 'string' && /[0-9A-Fa-f]/.test(c)
+    },
+}