feat: implement self-signed certificate support in API and UI

- Added support for self-signed TLS certificates in the ApiService, allowing configuration based on server settings.
- Introduced a toggle in the ServerConnectionPage to enable or disable trusting self-signed certificates.
- Updated localization files to include new strings for self-signed certificate settings in multiple languages.
- Enhanced the OptimizedStorageService to manage trusted servers based on user preferences for self-signed certificates.
- Improved error handling and logging throughout the affected services to ensure clarity and maintainability.

lib/l10n/app_de.arb

@@ -259,6 +259,14 @@
   "advancedSettings": "Erweiterte Einstellungen",
   "customHeaders": "Benutzerdefinierte Header",
   "customHeadersDescription": "Füge benutzerdefinierte HTTP-Header für Authentifizierung, API-Schlüssel oder spezielle Serveranforderungen hinzu.",
+  "allowSelfSignedCertificates": "Selbstsignierten Zertifikaten vertrauen",
+  "@allowSelfSignedCertificates": {
+    "description": "Schalterbeschriftung zum Zulassen selbstsignierter TLS-Zertifikate für den konfigurierten Server."
+  },
+  "allowSelfSignedCertificatesDescription": "Akzeptiere das TLS-Zertifikat dieses Servers auch dann, wenn es selbstsigniert ist. Aktiviere diese Option nur für Server, denen du vertraust.",
+  "@allowSelfSignedCertificatesDescription": {
+    "description": "Hilfetext, der die Risiken beim Aktivieren des Schalters für selbstsignierte Zertifikate erklärt."
+  },
   "headerNameEmpty": "Header-Name darf nicht leer sein",
   "headerNameTooLong": "Header-Name zu lang (max. 64 Zeichen)",
   "headerNameInvalidChars": "Ungültiger Header-Name. Verwende nur Buchstaben, Zahlen und diese Zeichen: !#$&-^_`|~",

lib/l10n/app_en.arb

@@ -550,6 +550,14 @@
   "@customHeaders": {"description": "Section title for adding custom HTTP headers."},
   "customHeadersDescription": "Add custom HTTP headers for authentication, API keys, or special server requirements.",
   "@customHeadersDescription": {"description": "Helper text explaining use-cases for custom headers."},
+  "allowSelfSignedCertificates": "Trust self-signed certificates",
+  "@allowSelfSignedCertificates": {
+    "description": "Toggle label that allows trusting self-signed TLS certificates for the configured server."
+  },
+  "allowSelfSignedCertificatesDescription": "Accept this server's TLS certificate even if it is self-signed. Enable only for servers you trust.",
+  "@allowSelfSignedCertificatesDescription": {
+    "description": "Helper text clarifying the risks of enabling the self-signed certificate toggle."
+  },
   "headerNameEmpty": "Header name cannot be empty",
   "@headerNameEmpty": {"description": "Validation message for empty header name."},
   "headerNameTooLong": "Header name too long (max 64 characters)",

lib/l10n/app_fr.arb

@@ -259,6 +259,14 @@
   "advancedSettings": "Paramètres avancés",
   "customHeaders": "En-têtes personnalisés",
   "customHeadersDescription": "Ajoutez des en-têtes HTTP personnalisés pour l'authentification, les clés API ou des exigences spécifiques du serveur.",
+  "allowSelfSignedCertificates": "Faire confiance aux certificats auto-signés",
+  "@allowSelfSignedCertificates": {
+    "description": "Libellé du commutateur permettant d'autoriser les certificats TLS auto-signés pour le serveur configuré."
+  },
+  "allowSelfSignedCertificatesDescription": "Acceptez le certificat TLS de ce serveur même s'il est auto-signé. Activez cette option uniquement pour les serveurs auxquels vous faites confiance.",
+  "@allowSelfSignedCertificatesDescription": {
+    "description": "Texte d'aide expliquant les risques liés à l'activation de l'option de certificat auto-signé."
+  },
   "headerNameEmpty": "Le nom de l'en-tête ne peut pas être vide",
   "headerNameTooLong": "Nom d'en-tête trop long (max 64 caractères)",
   "headerNameInvalidChars": "Nom d'en-tête invalide. Utilisez uniquement des lettres, des chiffres et ces symboles : !#$&-^_`|~",

lib/l10n/app_it.arb

@@ -259,6 +259,14 @@
   "advancedSettings": "Impostazioni avanzate",
   "customHeaders": "Header personalizzati",
   "customHeadersDescription": "Aggiungi header HTTP personalizzati per autenticazione, chiavi API o requisiti speciali del server.",
+  "allowSelfSignedCertificates": "Considera attendibili i certificati autofirmati",
+  "@allowSelfSignedCertificates": {
+    "description": "Etichetta dell'interruttore che consente i certificati TLS autofirmati per il server configurato."
+  },
+  "allowSelfSignedCertificatesDescription": "Accetta il certificato TLS di questo server anche se è autofirmato. Attiva questa opzione solo per server di cui ti fidi.",
+  "@allowSelfSignedCertificatesDescription": {
+    "description": "Testo di supporto che chiarisce i rischi dell'attivazione dell'opzione per certificati autofirmati."
+  },
   "headerNameEmpty": "Il nome header non può essere vuoto",
   "headerNameTooLong": "Nome header troppo lungo (max 64 caratteri)",
   "headerNameInvalidChars": "Nome header non valido. Usa solo lettere, numeri e questi simboli: !#$&-^_`|~",

lib/l10n/app_localizations.dart

@@ -1482,6 +1482,18 @@ abstract class AppLocalizations {
   /// **'Add custom HTTP headers for authentication, API keys, or special server requirements.'**
   String get customHeadersDescription;
 
+  /// Toggle label that allows trusting self-signed TLS certificates for the configured server.
+  ///
+  /// In en, this message translates to:
+  /// **'Trust self-signed certificates'**
+  String get allowSelfSignedCertificates;
+
+  /// Helper text clarifying the risks of enabling the self-signed certificate toggle.
+  ///
+  /// In en, this message translates to:
+  /// **'Accept this server\'s TLS certificate even if it is self-signed. Enable only for servers you trust.'**
+  String get allowSelfSignedCertificatesDescription;
+
   /// Validation message for empty header name.
   ///
   /// In en, this message translates to:

lib/l10n/app_localizations_de.dart

@@ -760,6 +760,14 @@ class AppLocalizationsDe extends AppLocalizations {
   String get customHeadersDescription =>
       'Füge benutzerdefinierte HTTP-Header für Authentifizierung, API-Schlüssel oder spezielle Serveranforderungen hinzu.';
 
+  @override
+  String get allowSelfSignedCertificates =>
+      'Selbstsignierten Zertifikaten vertrauen';
+
+  @override
+  String get allowSelfSignedCertificatesDescription =>
+      'Akzeptiere das TLS-Zertifikat dieses Servers auch dann, wenn es selbstsigniert ist. Aktiviere diese Option nur für Server, denen du vertraust.';
+
   @override
   String get headerNameEmpty => 'Header-Name darf nicht leer sein';
 

lib/l10n/app_localizations_en.dart

@@ -754,6 +754,13 @@ class AppLocalizationsEn extends AppLocalizations {
   String get customHeadersDescription =>
       'Add custom HTTP headers for authentication, API keys, or special server requirements.';
 
+  @override
+  String get allowSelfSignedCertificates => 'Trust self-signed certificates';
+
+  @override
+  String get allowSelfSignedCertificatesDescription =>
+      'Accept this server\'s TLS certificate even if it is self-signed. Enable only for servers you trust.';
+
   @override
   String get headerNameEmpty => 'Header name cannot be empty';
 

lib/l10n/app_localizations_fr.dart

@@ -765,6 +765,14 @@ class AppLocalizationsFr extends AppLocalizations {
   String get customHeadersDescription =>
       'Ajoutez des en-têtes HTTP personnalisés pour l\'authentification, les clés API ou des exigences spécifiques du serveur.';
 
+  @override
+  String get allowSelfSignedCertificates =>
+      'Faire confiance aux certificats auto-signés';
+
+  @override
+  String get allowSelfSignedCertificatesDescription =>
+      'Acceptez le certificat TLS de ce serveur même s\'il est auto-signé. Activez cette option uniquement pour les serveurs auxquels vous faites confiance.';
+
   @override
   String get headerNameEmpty => 'Le nom de l\'en-tête ne peut pas être vide';
 

lib/l10n/app_localizations_it.dart

@@ -756,6 +756,14 @@ class AppLocalizationsIt extends AppLocalizations {
   String get customHeadersDescription =>
       'Aggiungi header HTTP personalizzati per autenticazione, chiavi API o requisiti speciali del server.';
 
+  @override
+  String get allowSelfSignedCertificates =>
+      'Considera attendibili i certificati autofirmati';
+
+  @override
+  String get allowSelfSignedCertificatesDescription =>
+      'Accetta il certificato TLS di questo server anche se è autofirmato. Attiva questa opzione solo per server di cui ti fidi.';
+
   @override
   String get headerNameEmpty => 'Il nome header non può essere vuoto';