feat: Add community management features with QR code scanning

- Implement Community model for managing community data, including secret handling and PSK derivation.
- Create CommunityQrScannerScreen for scanning and joining communities via QR codes.
- Develop CommunityStore for persisting community data using SharedPreferences.
- Introduce QrCodeDisplay widget for displaying QR codes with customizable options.
- Add QrScannerWidget for reusable QR code scanning functionality with validation and controls.

pubspec.lock

@@ -453,6 +453,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.0"
+  mobile_scanner:
+    dependency: "direct main"
+    description:
+      name: mobile_scanner
+      sha256: "0b466a0a8a211b366c2e87f3345715faef9b6011c7147556ad22f37de6ba3173"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.0.11"
   nested:
     dependency: transitive
     description:
@@ -605,6 +613,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.1.5+1"
+  qr:
+    dependency: transitive
+    description:
+      name: qr
+      sha256: "5a1d2586170e172b8a8c8470bbbffd5eb0cd38a66c0d77155ea138d3af3a4445"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.2"
+  qr_flutter:
+    dependency: "direct main"
+    description:
+      name: qr_flutter
+      sha256: "5095f0fc6e3f71d08adef8feccc8cea4f12eec18a2e31c2e8d82cb6019f4b097"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.1.0"
   rxdart:
     dependency: transitive
     description: