Add configurable working directory for dev server scripts (Vibe Kanban) (#1559)

* The implementation is complete. Here's a summary of all the changes made:

## Summary

Added the ability for users to specify a working directory for dev server scripts:

### Files Changed:

1. **Database migration** - `crates/db/migrations/20251216000000_add_dev_script_working_dir_to_projects.sql`
   - Added `dev_script_working_dir TEXT DEFAULT ''` column

2. **Rust model** - `crates/db/src/models/project.rs`
   - Added `dev_script_working_dir` field to `Project` and `UpdateProject` structs
   - Updated all SQL queries

3. **Dev server execution** - `crates/server/src/routes/task_attempts.rs`
   - `start_dev_server` now passes `project.dev_script_working_dir` to the script executor

4. **Backfill logic** - `crates/services/src/services/container.rs`
   - Changed `backfill_repo_names` to set `dev_script_working_dir` instead of prepending `cd ./repo &&`

5. **Frontend UI** - `frontend/src/pages/settings/ProjectSettings.tsx`
   - Added input field for "Dev Server Working Directory"

6. **Translations** - `frontend/src/i18n/locales/en/settings.json`
   - Added `devWorkingDir` label, placeholder, and helper text

7. **TypeScript types** - `shared/types.ts`
   - Regenerated with `dev_script_working_dir` field

* Cleanup script changes for task attempt 83423e2d-0d45-47fb-a6e4-dd91a2140f91

* Both packages compile successfully. The fix is complete:

1. **`project.rs`**: Removed `.or()` fallback for `dev_script` and `dev_script_working_dir` so `None` now clears the field
2. **`container.rs`**: Updated backfill to explicitly pass the existing project name instead of `None`

* Done. I've completed both review tasks:

1. Removed the comment from `container.rs` line 384
2. Added `devWorkingDir` translations to all four language files (es, ja, ko, zh-Hans) with:
   - `label`: The field label
   - `placeholder`: Example placeholder text
   - `helper`: Description of what the field does

I also updated the `dev.helper` text in each language to reference the new working directory option instead of suggesting users manually `cd` into the repo directory.

* Done. Removed both comments:
1. Removed the comment from the migration file
2. Removed the comment from `task_attempts.rs` line 1267

* Fixed. The TypeScript error in `NoServerContent.tsx` has been resolved by adding `dev_script_working_dir: null` to the `UpdateProject` data. All checks pass:

- ✅ `npm run format` - completed
- ✅ `npm run lint` - passed (frontend and backend)
- ✅ `npx tsc --noEmit` - passed

* The Korean and Chinese translations already had the updated copy without the `cd` reference. The Spanish and Japanese were updated. All the translations now have the proper helper text that references the working directory field instead of telling users to manually `cd` into the repo.

* Done. I've removed the `cd my_website` line from both the Windows and Unix script placeholder examples in `scriptPlaceholders.ts`. Now the placeholder examples just show `npm run dev` without the `cd` command, since users can specify the working directory separately.

crates/server/src/routes/task_attempts.rs

@@ -1263,12 +1263,19 @@ pub async fn start_dev_server(
             )));
         }
     };
+
+    let working_dir = project
+        .dev_script_working_dir
+        .as_ref()
+        .filter(|dir| !dir.is_empty())
+        .cloned();
+
     let executor_action = ExecutorAction::new(
         ExecutorActionType::ScriptRequest(ScriptRequest {
             script: dev_script,
             language: ScriptRequestLanguage::Bash,
             context: ScriptContext::DevServer,
-            working_dir: None,
+            working_dir,
         }),
         None,
     );