feat(backup): add database reset action to account page

- Add reset() method to BackupService that deletes all 8 coffee tables
  in a transaction, respecting FK constraint order
- Add POST /api/v1/backup/reset endpoint (requires auth)
- Add "Reset Database" button with double-confirmation to account page
- Stack data buttons vertically on mobile for better layout

src/application/routes/api/backup.rs

@@ -58,3 +58,19 @@ pub(crate) async fn restore_backup(
     })?;
     Ok(StatusCode::NO_CONTENT.into_response())
 }
+
+/// POST /api/v1/backup/reset — delete all coffee data (requires authentication)
+pub(crate) async fn reset_database(
+    State(state): State<AppState>,
+    _auth_user: AuthenticatedUser,
+) -> Result<Response, ApiError> {
+    state
+        .backup_service
+        .reset()
+        .await
+        .map_err(|e| AppError::unexpected(e.to_string()))?;
+
+    tracing::info!("database reset: all coffee data deleted");
+
+    Ok(StatusCode::NO_CONTENT.into_response())
+}

src/application/routes/api/mod.rs

@@ -90,6 +90,7 @@ pub(super) fn router() -> axum::Router<AppState> {
             "/backup/restore",
             post(backup::restore_backup).layer(DefaultBodyLimit::max(50 * 1024 * 1024)),
         )
+        .route("/backup/reset", post(backup::reset_database))
 }
 
 pub(super) fn webauthn_router() -> axum::Router<AppState> {

src/infrastructure/backup.rs

@@ -115,6 +115,44 @@ impl BackupService {
         Ok(())
     }
 
+    /// Delete all coffee data, leaving auth tables intact.
+    ///
+    /// After a successful reset the database is in the same state that
+    /// `verify_empty_database()` requires, so a subsequent `restore()` will
+    /// succeed.
+    pub async fn reset(&self) -> anyhow::Result<()> {
+        let mut tx = self
+            .pool
+            .begin()
+            .await
+            .context("failed to begin transaction")?;
+
+        // Delete in FK-safe order: children before parents.
+        // brews has RESTRICT FK → gear; cups has RESTRICT FK → roasts, cafes.
+        let tables = [
+            "brews",
+            "cups",
+            "bags",
+            "roasts",
+            "timeline_events",
+            "gear",
+            "cafes",
+            "roasters",
+        ];
+
+        for table in tables {
+            let query = format!("DELETE FROM {table}");
+            sqlx::query(&query)
+                .execute(&mut *tx)
+                .await
+                .with_context(|| format!("failed to delete from {table}"))?;
+        }
+
+        tx.commit().await.context("failed to commit transaction")?;
+
+        Ok(())
+    }
+
     // --- Export methods ---
 
     async fn export_roasters(&self) -> anyhow::Result<Vec<Roaster>> {

templates/pages/account.html

@@ -224,11 +224,11 @@
       <p class="mt-1 text-sm text-text-secondary">Export all coffee data as JSON, restore from a previous backup, or reset to start fresh.</p>
     </div>
 
-    <div class="flex flex-wrap gap-3">
+    <div class="flex flex-col gap-3 sm:flex-row sm:flex-wrap">
       <a
         href="/api/v1/backup"
         download
-        class="rounded-md bg-accent px-4 py-2 text-sm font-medium text-accent-text transition hover:bg-accent-hover inline-block"
+        class="rounded-md bg-accent px-4 py-2 text-center text-sm font-medium text-accent-text transition hover:bg-accent-hover"
       >
         Download Backup
       </a>

tests/server/backup.rs

@@ -631,3 +631,89 @@ async fn backup_round_trip_via_api() {
     assert_eq!(roasters.len(), 1);
     assert_eq!(roasters[0].name, "Test Roasters");
 }
+
+// --- Reset tests ---
+
+#[tokio::test]
+async fn reset_requires_auth() {
+    let app = spawn_app().await;
+    let client = reqwest::Client::new();
+
+    let response = client
+        .post(app.api_url("/backup/reset"))
+        .send()
+        .await
+        .expect("failed to send request");
+
+    assert_eq!(response.status(), reqwest::StatusCode::UNAUTHORIZED);
+}
+
+#[tokio::test]
+async fn reset_clears_all_data() {
+    let db = create_test_db().await;
+    populate_test_data(&db).await;
+
+    // Verify data exists before reset
+    assert!(!list_all_roasters(db.roaster_repo.as_ref()).await.is_empty());
+    assert!(!list_all_roasts(db.roast_repo.as_ref()).await.is_empty());
+    assert!(!list_all_bags(db.bag_repo.as_ref()).await.is_empty());
+    assert!(!list_all_gear(db.gear_repo.as_ref()).await.is_empty());
+    assert!(!list_all_brews(db.brew_repo.as_ref()).await.is_empty());
+    assert!(!list_all_cafes(db.cafe_repo.as_ref()).await.is_empty());
+    assert!(
+        !list_all_timeline_events(db.timeline_repo.as_ref())
+            .await
+            .is_empty()
+    );
+
+    // Reset
+    db.backup_service
+        .reset()
+        .await
+        .expect("failed to reset database");
+
+    // Verify all tables are empty
+    assert!(list_all_roasters(db.roaster_repo.as_ref()).await.is_empty());
+    assert!(list_all_roasts(db.roast_repo.as_ref()).await.is_empty());
+    assert!(list_all_bags(db.bag_repo.as_ref()).await.is_empty());
+    assert!(list_all_gear(db.gear_repo.as_ref()).await.is_empty());
+    assert!(list_all_brews(db.brew_repo.as_ref()).await.is_empty());
+    assert!(list_all_cafes(db.cafe_repo.as_ref()).await.is_empty());
+    assert!(
+        list_all_timeline_events(db.timeline_repo.as_ref())
+            .await
+            .is_empty()
+    );
+}
+
+#[tokio::test]
+async fn reset_then_restore_succeeds() {
+    let db = create_test_db().await;
+    populate_test_data(&db).await;
+
+    // Export before reset
+    let backup = db.backup_service.export().await.expect("failed to export");
+    assert_eq!(backup.roasters.len(), 1);
+    assert_eq!(backup.gear.len(), 3);
+    assert_eq!(backup.brews.len(), 1);
+
+    // Reset
+    db.backup_service
+        .reset()
+        .await
+        .expect("failed to reset database");
+
+    // Restore should succeed (database is now empty)
+    db.backup_service
+        .restore(backup)
+        .await
+        .expect("failed to restore after reset");
+
+    // Verify data is back
+    assert_eq!(list_all_roasters(db.roaster_repo.as_ref()).await.len(), 1);
+    assert_eq!(list_all_roasts(db.roast_repo.as_ref()).await.len(), 1);
+    assert_eq!(list_all_bags(db.bag_repo.as_ref()).await.len(), 1);
+    assert_eq!(list_all_gear(db.gear_repo.as_ref()).await.len(), 3);
+    assert_eq!(list_all_brews(db.brew_repo.as_ref()).await.len(), 1);
+    assert_eq!(list_all_cafes(db.cafe_repo.as_ref()).await.len(), 1);
+}