Parse custom_recovery_passphrase_settings from Element .well-known

Add CustomRecoveryPassphraseRequirements to ElementWellKnown and decode
the custom_recovery_passphrase_settings block (currently just
min_character_count) from the homeserver's element.json. Invalid specs
(missing or non-positive min_character_count) are logged and mapped to
null so the setup flow falls back to the generated-key path. Field names
match the ESS well-known schema (element-enterprise#261).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

libraries/wellknown/test/src/main/kotlin/io/element/android/features/wellknown/test/Fixtures.kt

@@ -8,6 +8,7 @@
 
 package io.element.android.features.wellknown.test
 
+import io.element.android.libraries.wellknown.api.CustomRecoveryPassphraseRequirements
 import io.element.android.libraries.wellknown.api.ElementWellKnown
 
 fun anElementWellKnown(
@@ -17,6 +18,7 @@ fun anElementWellKnown(
     brandColor: String? = null,
     notificationSound: String? = null,
     identityProviderAppScheme: String? = null,
+    customRecoveryPassphraseRequirements: CustomRecoveryPassphraseRequirements? = null,
 ) = ElementWellKnown(
     registrationHelperUrl = registrationHelperUrl,
     enforceElementPro = enforceElementPro,
@@ -24,4 +26,11 @@ fun anElementWellKnown(
     brandColor = brandColor,
     notificationSound = notificationSound,
     identityProviderAppScheme = identityProviderAppScheme,
+    customRecoveryPassphraseRequirements = customRecoveryPassphraseRequirements,
+)
+
+fun aCustomRecoveryPassphraseRequirements(
+    minCharacterCount: Int = 8,
+) = CustomRecoveryPassphraseRequirements(
+    minCharacterCount = minCharacterCount,
 )