docs: translate all code comments to English (language policy)

Translate every Italian /// XML doc comment, <!-- --> XAML comment, and
// inline comment to English across all source files (Core, App, tests).
Add the language policy to CLAUDE.md (conversation Italian; all code
and docs English). Update one test assertion that checked an Italian
exception message that was also translated.

src/Core/Crypto/DerivationPaths.cs

@@ -4,25 +4,25 @@ using PalladiumWallet.Core.Chain;
 namespace PalladiumWallet.Core.Crypto;
 
 /// <summary>
-/// Costruzione dei derivation path BIP44/49/84 (blueprint §4.2) e mappatura
-/// ScriptKind → purpose / ScriptPubKeyType. I purpose sono costanti di protocollo
-/// BIP (chain-independent); il coin_type viene sempre dal ChainProfile.
+/// BIP44/49/84 derivation path construction (blueprint §4.2) and mapping of
+/// ScriptKind → purpose / ScriptPubKeyType. Purposes are BIP protocol constants
+/// (chain-independent); coin_type always comes from the ChainProfile.
 /// </summary>
 public static class DerivationPaths
 {
-    /// <summary>Purpose BIP44 (P2PKH legacy).</summary>
+    /// <summary>BIP44 purpose (P2PKH legacy).</summary>
     public const int PurposeLegacy = 44;
 
-    /// <summary>Purpose BIP49 (P2SH-P2WPKH).</summary>
+    /// <summary>BIP49 purpose (P2SH-P2WPKH).</summary>
     public const int PurposeWrappedSegwit = 49;
 
-    /// <summary>Purpose BIP84 (P2WPKH nativo).</summary>
+    /// <summary>BIP84 purpose (native P2WPKH).</summary>
     public const int PurposeNativeSegwit = 84;
 
-    /// <summary>Purpose BIP48 (multisig — fase successiva, §16 passo 8).</summary>
+    /// <summary>BIP48 purpose (multisig — next phase, §16 step 8).</summary>
     public const int PurposeMultisig = 48;
 
-    /// <summary>Purpose BIP86 (P2TR key-path, Taproot).</summary>
+    /// <summary>BIP86 purpose (P2TR key-path, Taproot).</summary>
     public const int PurposeTaproot = 86;
 
     public static int PurposeFor(ScriptKind kind) => kind switch
@@ -36,9 +36,9 @@ public static class DerivationPaths
     };
 
     /// <summary>
-    /// Tipo di scriptPubKey NBitcoin per la derivazione da pubkey singola.
-    /// I tipi multisig derivano da redeem script, non da una pubkey: arriveranno
-    /// con i wallet M-di-N (§4.5).
+    /// NBitcoin scriptPubKey type for single-pubkey derivation.
+    /// Multisig types are derived from a redeem script, not a pubkey — they will
+    /// arrive with M-of-N wallet support (§4.5).
     /// </summary>
     public static ScriptPubKeyType ScriptPubKeyTypeFor(ScriptKind kind) => kind switch
     {
@@ -48,13 +48,13 @@ public static class DerivationPaths
         ScriptKind.Taproot => ScriptPubKeyType.TaprootBIP86,
         ScriptKind.WrappedSegwitMultisig or ScriptKind.NativeSegwitMultisig =>
             throw new NotSupportedException(
-                "I tipi multisig derivano da redeem script: supporto previsto con i wallet M-di-N (§4.5)."),
+                "Multisig types are derived from a redeem script: support planned with M-of-N wallets (§4.5)."),
         _ => throw new ArgumentOutOfRangeException(nameof(kind)),
     };
 
     /// <summary>
-    /// Path di account relativo alla root: purpose'/coin'/account' (§4.2).
-    /// Il coin_type è quello del profilo (746 mainnet, 1 testnet).
+    /// Account path relative to the root: purpose'/coin'/account' (§4.2).
+    /// coin_type is taken from the profile (746 mainnet, 1 testnet).
     /// </summary>
     public static KeyPath AccountPath(ScriptKind kind, ChainProfile profile, int account = 0)
     {
@@ -64,7 +64,7 @@ public static class DerivationPaths
             $"{PurposeFor(kind)}'/{profile.Bip44CoinType}'/{account}'");
     }
 
-    /// <summary>Sottopath non-hardened change/index sotto l'account (change=0 receiving, change=1 change).</summary>
+    /// <summary>Non-hardened change/index sub-path under the account (change=0 receiving, change=1 change).</summary>
     public static KeyPath AddressSubPath(bool isChange, int index)
     {
         if (index < 0)
@@ -73,8 +73,8 @@ public static class DerivationPaths
     }
 
     /// <summary>
-    /// Parsing di derivation path personalizzati in import (Sparrow-like, §4.2):
-    /// accetta il prefisso "m/" opzionale e gli hardened marker ' oppure h.
+    /// Parsing of custom derivation paths on import (Sparrow-like, §4.2):
+    /// accepts the optional "m/" prefix and hardened markers ' or h.
     /// </summary>
     public static bool TryParse(string path, out KeyPath? keyPath)
     {