extract Nip05OrPubkeyLine into shared composable

Extract nip05 value calculation into helper

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip05DnsIdentifiers/Nip05Id.kt

@@ -29,6 +29,13 @@ data class Nip05Id(
 ) {
     fun toValue(): String = assemble(name, domain)
 
+    /**
+     * Renders the address for users to read. When [name] is `"_"`, NIP-05
+     * specifies the address should display as just the domain. Use this in UI;
+     * use [toValue] for network lookups and storage.
+     */
+    fun toDisplayValue(): String = if (name == "_") domain else assemble(name, domain)
+
     fun toUserUrl(): String = userUrl(name, domain)
 
     fun toDomainUrl(): String = domainUrl(domain)

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip05DnsIdentifiers/Nip05Test.kt

@@ -109,6 +109,20 @@ class Nip05Test {
         assertEquals("https://$domain/.well-known/nostr.json", parsedNip05.toDomainUrl())
     }
 
+    @Test
+    fun `toDisplayValue with regular name returns name@domain`() {
+        val nip05 = Nip05Id.parse("alice@example.com")
+        assertNotNull(nip05)
+        assertEquals("alice@example.com", nip05.toDisplayValue())
+    }
+
+    @Test
+    fun `toDisplayValue with underscore name returns domain only`() {
+        val nip05 = Nip05Id.parse("_@example.com")
+        assertNotNull(nip05)
+        assertEquals("example.com", nip05.toDisplayValue())
+    }
+
     @Test
     fun `test json parsing with relays`() {
         val parsedNip05 = Nip05Id.parse("bob@test.com")