fix(ui): reader Reply quotes original + guard one-shot actions against double-tap

#303: the reader's Reply now routes through MailRepository.buildReplyDraft
(quotes the original into a <blockquote>, bakes the signature, prefixes Re:/Fwd:
without double-prefixing) and opens compose on the built draft via
ReaderEvent.OpenCompose — the same high-fidelity path the mailbox uses — instead
of a bare compose prefill with an empty body. Adds Reply-All and Forward via an
app-bar overflow menu.

#304: SignatureEditViewModel.save, ReportReviewViewModel.submit,
AccountSettingsViewModel.removeAccount, and ProblemReportsViewModel.createManualReport
now flip a busy/saving flag synchronously before the first suspension and gate
their buttons, so a rapid double-tap can't create duplicate signatures/reports,
enqueue two uploads, or over-pop the back stack.

Closes #303
Closes #304

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/androidTest/kotlin/org/libremail/ui/reader/ReaderScreenTest.kt

@@ -11,6 +11,7 @@ import androidx.compose.ui.test.performClick
 import androidx.lifecycle.SavedStateHandle
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Assert.assertEquals
 import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -18,6 +19,7 @@ import org.libremail.R
 import org.libremail.data.settings.SettingsRepository
 import org.libremail.domain.model.Attachment
 import org.libremail.domain.model.Message
+import org.libremail.domain.model.ReplyMode
 import org.libremail.ui.FakeMailRepository
 import org.libremail.ui.navigation.Routes
 import org.libremail.ui.theme.LibreMailTheme
@@ -44,8 +46,17 @@ class ReaderScreenTest {
     private fun attachment(partIndex: Int, filename: String) =
         Attachment(messageId, partIndex, filename, "application/pdf", 1_000L)
 
-    /** Renders [ReaderScreen] for the fixed [message] with the given [attachments] and awaits load. */
-    private fun renderReader(attachments: List<Attachment>, downloadedParts: Set<Int> = emptySet()) {
+    /** The draft id the reader last asked to open compose on (via OpenCompose), or null. */
+    private var openedDraftId: String? = null
+
+    /**
+     * Renders [ReaderScreen] for the fixed [message] with the given [attachments], awaits load, and
+     * returns the backing [FakeMailRepository] so a test can assert which reply drafts were built.
+     */
+    private fun renderReader(
+        attachments: List<Attachment> = emptyList(),
+        downloadedParts: Set<Int> = emptySet(),
+    ): FakeMailRepository {
         val context = InstrumentationRegistry.getInstrumentation().targetContext.applicationContext
         val repo = FakeMailRepository(
             messages = listOf(message),
@@ -59,12 +70,14 @@ class ReaderScreenTest {
         )
         composeTestRule.setContent {
             LibreMailTheme(darkTheme = false, dynamicColor = false) {
-                ReaderScreen(onBack = {}, onReply = { _, _, _ -> }, viewModel = viewModel)
+                ReaderScreen(onBack = {}, onOpenCompose = { openedDraftId = it }, viewModel = viewModel)
             }
         }
+        // The Reply action appears once the message loads, regardless of whether it has attachments.
         composeTestRule.waitUntil(5_000) {
-            composeTestRule.onAllNodesWithText(attachments.first().filename).fetchSemanticsNodes().isNotEmpty()
+            composeTestRule.onAllNodesWithText(string(R.string.reader_reply)).fetchSemanticsNodes().isNotEmpty()
         }
+        return repo
     }
 
     @Test
@@ -111,4 +124,39 @@ class ReaderScreenTest {
         composeTestRule.onNodeWithText(seeMore(1)).assertIsDisplayed()
         composeTestRule.onNodeWithText("b.pdf").assertDoesNotExist()
     }
+
+    @Test
+    fun reader_reply_buildsQuotedReplyDraftAndOpensCompose() {
+        val repo = renderReader()
+
+        composeTestRule.onNodeWithText(string(R.string.reader_reply)).performClick()
+        composeTestRule.waitUntil(5_000) { openedDraftId != null }
+
+        // The reader routes through buildReplyDraft (quotes the original + bakes the signature),
+        // not a bare compose prefill (#303), and opens compose on the resulting draft.
+        assertEquals(listOf(messageId to ReplyMode.REPLY), repo.replyDrafts)
+        assertEquals("draft-$messageId", openedDraftId)
+    }
+
+    @Test
+    fun reader_forward_viaOverflow_buildsForwardDraft() {
+        val repo = renderReader()
+
+        composeTestRule.onNodeWithContentDescription(string(R.string.action_more)).performClick()
+        composeTestRule.onNodeWithText(string(R.string.action_forward)).performClick()
+        composeTestRule.waitUntil(5_000) { openedDraftId != null }
+
+        assertEquals(listOf(messageId to ReplyMode.FORWARD), repo.replyDrafts)
+    }
+
+    @Test
+    fun reader_replyAll_viaOverflow_buildsReplyAllDraft() {
+        val repo = renderReader()
+
+        composeTestRule.onNodeWithContentDescription(string(R.string.action_more)).performClick()
+        composeTestRule.onNodeWithText(string(R.string.action_reply_all)).performClick()
+        composeTestRule.waitUntil(5_000) { openedDraftId != null }
+
+        assertEquals(listOf(messageId to ReplyMode.REPLY_ALL), repo.replyDrafts)
+    }
 }