huge refacto of the permissions handling + fix various regression

/**
 * Keeps permissionsStore aligned with the browser. The store is a cache,
 * never a second source of truth: every signal re-reads the browser via
 * syncPermissions() (single writer).
 *
 * Re-sync triggers, all event-driven — no polling:
 *  - devicechange: granting permission reveals device labels/ids, so this
 *    fires on grant in every browser INCLUDING Safari — replacing the
 *    previous 500ms Safari polling. (A denial is caught by the concurrent
 *    getUserMedia rejection → notePermissionDeniedFromGum.)
 *  - window focus: returning from the browser/system permission UI.
 *  - Permissions API 'change' events, where the query is supported.
 */

src/frontend/package.json

@@ -29,7 +29,6 @@
     "@tanstack/react-query": "5.101.1",
     "@timephy/rnnoise-wasm": "1.0.0",
     "crisp-sdk-web": "1.1.2",
-    "derive-valtio": "0.2.0",
     "hoofd": "1.7.3",
     "humanize-duration": "3.33.2",
     "i18next": "26.3.1",