Release Preview 20 shared desktop, Android and Sargo updates

Restore Gaia settings and media workflows, extend native network adapters, and align the APK payload. Generate French/English changelogs and website entries from the simplified JSON source.

Validation: shared JS and Tundra unit tests; desktop workflows and persistence; signed APK payload parity; Sargo RAM and installed startup with boot readback. Android runtime qualification is recorded separately.

release.json

@@ -1,15 +1,15 @@
 {
   "gaia": "2.7.0",
   "channel": "preview",
-  "revision": 17,
-  "androidVersionCode": 17,
+  "revision": 20,
+  "androidVersionCode": 20,
   "geckoview": "156.0.20260921121718",
   "engineAlignment": {
     "family": "156",
     "patchParity": false,
     "reason": "Firefox desktop 156.0.1; Mozilla's GeckoView release repository currently offers 156.0 only. Keep the desktop patch and report actual engine versions."
   },
-  "version": "2.7-preview.17",
+  "version": "2.7-preview.20",
   "adapters": {
     "desktop": "0.1.0-dev",
     "android": "0.1.0-dev"