fork: initialize Mycellium UI Private from Mycell-UI@5229e2c

This repo is a hard fork of mycellium-ui dedicated to the
mycelium-private experimental track upstream. The two apps coexist
on the same machine via distinct app identifiers, polkit actions,
and binary names.

Renames
- package + crate: mycellium-ui → mycellium-ui-private
- bundle identifier: tech.threefold.mycellium-ui-private
- daemon binary: mycelium-private (separate upstream release tarball)
- bootstrap wrapper: /usr/bin/mycellium-bootstrap-private
- polkit policy file + action id

Functional changes
- SidecarConfig.network_name field (UTF-8, 2..=64 bytes)
- start() refuses to spawn without a network name AND a 32-byte
  key file at app_data_dir/network_key.bin; surfaces a clear
  error rather than letting mycelium-private fail mid-startup
- network_key_status / generate / import / export / delete
  commands; uses OS RNG (rand) and writes 0600
- empty default peers list (no Threefold seed for private overlays)
- new Settings → Private network panel: name input, key generate /
  reveal-hex / import / delete, status indicator

Adapted bootstrap script kills both `mycelium` and
`mycelium-private` orphans (cross-clash on UDP/9650 + TCP/8990).

CI workflow + sidebar branding updated. The README explains the
divergence model and how to cherry-pick upstream fixes.

src-tauri/tauri.conf.json

@@ -1,8 +1,8 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
-  "productName": "Mycellium UI",
+  "productName": "Mycellium UI Private",
   "version": "0.1.0",
-  "identifier": "tech.threefold.mycellium-ui",
+  "identifier": "tech.threefold.mycellium-ui-private",
   "build": {
     "beforeDevCommand": "pnpm dev",
     "devUrl": "http://localhost:1420",
@@ -14,7 +14,7 @@
     "windows": [
       {
         "label": "main",
-        "title": "Mycellium",
+        "title": "Mycellium Private",
         "width": 1100,
         "height": 720,
         "minWidth": 800,
@@ -30,20 +30,20 @@
     "active": true,
     "targets": ["deb", "appimage"],
     "category": "Utility",
-    "shortDescription": "Mycelium overlay network client",
-    "longDescription": "Desktop GUI for the Mycelium end-to-end encrypted IPv6 overlay network.",
+    "shortDescription": "Mycelium private network client",
+    "longDescription": "Desktop GUI for joining a private Mycelium overlay network — a self-contained IPv6 mesh isolated from the public Mycelium network by a shared 32-byte key.",
     "icon": [
       "icons/32x32.png",
       "icons/128x128.png",
       "icons/128x128@2x.png"
     ],
-    "externalBin": ["binaries/mycelium"],
+    "externalBin": ["binaries/mycelium-private"],
     "linux": {
       "deb": {
         "depends": ["pkexec | policykit-1"],
         "files": {
-          "/usr/share/polkit-1/actions/tech.threefold.mycellium-ui.policy": "packaging/polkit/tech.threefold.mycellium-ui.policy",
-          "/usr/bin/mycellium-bootstrap": "packaging/mycellium-bootstrap"
+          "/usr/share/polkit-1/actions/tech.threefold.mycellium-ui-private.policy": "packaging/polkit/tech.threefold.mycellium-ui-private.policy",
+          "/usr/bin/mycellium-bootstrap-private": "packaging/mycellium-bootstrap-private"
         }
       }
     }