Add enterprise gate for custom recovery passphrase

Add isCustomRecoveryPassphraseEnabled() and
estimateCustomRecoveryPassphraseStrength() to EnterpriseService, plus the
CustomRecoveryPassphraseStrength result types. FOSS builds return
false/null so the feature stays gated off; the enterprise implementation
(estimator) lands separately in the enterprise repo.

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

features/enterprise/api/src/main/kotlin/io/element/android/features/enterprise/api/CustomRecoveryPassphraseStrength.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.enterprise.api
+
+/**
+ * Strength tier surfaced to the user under a custom recovery passphrase field.
+ * The eight tiers mirror iOS `PasswordStrengthThreshold` 1:1 so both clients label a given
+ * passphrase identically; each maps to its own label and time-to-crack description in the UI.
+ */
+enum class CustomRecoveryPassphraseStrength {
+    Garbage,
+    Weak,
+    Moderate,
+    Okay,
+    Strong,
+    VeryStrong,
+    UltraStrong,
+    Mega,
+}
+
+/**
+ * Result of estimating a custom recovery passphrase's strength. The estimation algorithm itself
+ * is an enterprise capability ([EnterpriseService.estimateCustomRecoveryPassphraseStrength]); FOSS
+ * builds never produce one.
+ */
+data class CustomRecoveryPassphraseStrengthResult(
+    val strength: CustomRecoveryPassphraseStrength,
+    /** Fill amount for the progress bar. Always in `0f..1f`. */
+    val score: Float,
+)

features/enterprise/api/src/main/kotlin/io/element/android/features/enterprise/api/EnterpriseService.kt

@@ -41,6 +41,22 @@ interface EnterpriseService {
      */
     fun getNoisyNotificationChannelId(sessionId: SessionId): String?
 
+    /**
+     * Whether the user is allowed to set a custom recovery passphrase.
+     * Enterprise builds gate this in addition to the homeserver's .well-known `customRecoveryPassphraseRequirements`;
+     * when false the setup flow falls back to the auto-generated key path even if the homeserver
+     * advertises a spec.
+     */
+    fun isCustomRecoveryPassphraseEnabled(): Boolean
+
+    /**
+     * Estimate the strength of a user-typed custom recovery [passphrase].
+     * The estimation algorithm is an enterprise capability: FOSS builds return null, so callers
+     * should treat null as "no indicator to show". Callers are responsible for not calling this with
+     * an empty passphrase if they want the indicator hidden while the field is empty.
+     */
+    fun estimateCustomRecoveryPassphraseStrength(passphrase: String): CustomRecoveryPassphraseStrengthResult?
+
     companion object {
         const val ANY_ACCOUNT_PROVIDER = "*"
     }

features/enterprise/impl-foss/src/main/kotlin/io/element/android/features/enterprise/impl/DefaultEnterpriseService.kt

@@ -13,6 +13,7 @@ import dev.zacsweers.metro.AppScope
 import dev.zacsweers.metro.ContributesBinding
 import io.element.android.compound.colors.SemanticColorsLightDark
 import io.element.android.features.enterprise.api.BugReportUrl
+import io.element.android.features.enterprise.api.CustomRecoveryPassphraseStrengthResult
 import io.element.android.features.enterprise.api.EnterpriseService
 import io.element.android.libraries.matrix.api.core.SessionId
 import kotlinx.coroutines.flow.Flow
@@ -45,4 +46,8 @@ class DefaultEnterpriseService : EnterpriseService {
     }
 
     override fun getNoisyNotificationChannelId(sessionId: SessionId): String? = null
+
+    override fun isCustomRecoveryPassphraseEnabled(): Boolean = false
+
+    override fun estimateCustomRecoveryPassphraseStrength(passphrase: String): CustomRecoveryPassphraseStrengthResult? = null
 }

features/enterprise/test/src/main/kotlin/io/element/android/features/enterprise/test/FakeEnterpriseService.kt

@@ -11,6 +11,7 @@ package io.element.android.features.enterprise.test
 import androidx.compose.ui.graphics.Color
 import io.element.android.compound.colors.SemanticColorsLightDark
 import io.element.android.features.enterprise.api.BugReportUrl
+import io.element.android.features.enterprise.api.CustomRecoveryPassphraseStrengthResult
 import io.element.android.features.enterprise.api.EnterpriseService
 import io.element.android.libraries.matrix.api.core.SessionId
 import io.element.android.tests.testutils.lambda.lambdaError
@@ -31,6 +32,8 @@ class FakeEnterpriseService(
     private val unifiedPushDefaultPushGatewayResult: () -> String? = { lambdaError() },
     private val getNoisyNotificationChannelIdResult: (SessionId?) -> String? = { lambdaError() },
     private val tweakMasUrlResult: (String, String) -> String = { _, _ -> lambdaError() },
+    private val isCustomRecoveryPassphraseEnabledResult: Boolean = false,
+    private val estimateCustomRecoveryPassphraseStrengthResult: (String) -> CustomRecoveryPassphraseStrengthResult? = { null },
 ) : EnterpriseService {
     private val brandColorState = MutableStateFlow(initialBrandColor)
     private val semanticColorsState = MutableStateFlow(initialSemanticColors)
@@ -79,4 +82,9 @@ class FakeEnterpriseService(
     override fun getNoisyNotificationChannelId(sessionId: SessionId): String? {
         return getNoisyNotificationChannelIdResult(sessionId)
     }
+
+    override fun isCustomRecoveryPassphraseEnabled(): Boolean = isCustomRecoveryPassphraseEnabledResult
+
+    override fun estimateCustomRecoveryPassphraseStrength(passphrase: String): CustomRecoveryPassphraseStrengthResult? =
+        estimateCustomRecoveryPassphraseStrengthResult(passphrase)
 }