Add project soft-delete with workspace archival

- Add delete button (×) to sidebar project list, shown on hover
- Soft-delete: mark projects as deleted in DB instead of hard delete
- Move workspace files to /app/data/deleted/ folder on deletion
- Filter deleted projects from list query
- Auto-select next project after deleting current one
- Also includes agent prompt improvements for reverse proxy paths

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/api/projects.rs

@@ -40,7 +40,7 @@ pub fn router(state: Arc<AppState>) -> Router {
 async fn list_projects(
     State(state): State<Arc<AppState>>,
 ) -> ApiResult<Vec<Project>> {
-    sqlx::query_as::<_, Project>("SELECT * FROM projects ORDER BY updated_at DESC")
+    sqlx::query_as::<_, Project>("SELECT * FROM projects WHERE deleted = 0 ORDER BY updated_at DESC")
         .fetch_all(&state.db.pool)
         .await
         .map(Json)
@@ -109,10 +109,30 @@ async fn delete_project(
     State(state): State<Arc<AppState>>,
     Path(id): Path<String>,
 ) -> ApiResult<bool> {
-    sqlx::query("DELETE FROM projects WHERE id = ?")
+    // Soft delete: mark as deleted in DB
+    let result = sqlx::query("UPDATE projects SET deleted = 1, updated_at = datetime('now') WHERE id = ? AND deleted = 0")
         .bind(&id)
         .execute(&state.db.pool)
         .await
-        .map(|r| Json(r.rows_affected() > 0))
-        .map_err(db_err)
+        .map_err(db_err)?;
+
+    if result.rows_affected() == 0 {
+        return Ok(Json(false));
+    }
+
+    // Move workspace to deleted folder
+    let src = std::path::PathBuf::from("/app/data/workspaces").join(&id);
+    let dst_dir = std::path::PathBuf::from("/app/data/deleted");
+    if src.exists() {
+        if let Err(e) = tokio::fs::create_dir_all(&dst_dir).await {
+            tracing::error!("Failed to create deleted dir: {}", e);
+        } else {
+            let dst = dst_dir.join(&id);
+            if let Err(e) = tokio::fs::rename(&src, &dst).await {
+                tracing::error!("Failed to move workspace to deleted: {}", e);
+            }
+        }
+    }
+
+    Ok(Json(true))
 }