Feat: confluence space key (#11706)

# PR Description: Add Space Key Configuration for Confluence Data Source

### What problem does this PR solve?

This PR addresses issue #11638 where users requested the ability to
specify Confluence Space Keys when configuring a Confluence data source
connector.

**Problem:**
Currently, the RAGFlow UI for Confluence data sources only provides
fields for:
- Username
- Access Token  
- Wiki Base URL
- Is Cloud checkbox

There is no way to specify which Confluence space(s) to sync, causing
RAGFlow to attempt syncing all accessible spaces. This is problematic
for users who:
- Only want to index specific spaces (e.g., only the HR or Documentation
space)
- Have access to many spaces but only need a subset
- Want to avoid unnecessary data transfer and processing

**Solution:**
The backend `ConfluenceConnector` class already supports a `space`
parameter in its `__init__()` method (line 1282 in
`common/data_source/confluence_connector.py`), but this parameter was
never exposed in the UI. This PR adds the missing UI field to allow
users to configure space filtering.

**User Impact:**
Users can now:
- Leave the field empty to sync all accessible spaces (default behavior)
- Specify a single space key (e.g., `DEV`)
- Specify multiple space keys separated by commas (e.g., `DEV,DOCS,HR`)

This gives users fine-grained control over which Confluence content gets
indexed into their RAGFlow knowledge base.

Fixes #11638

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---

## Implementation Details

### Changes Made

**1. Frontend UI
(`web/src/pages/user-setting/data-source/contant.tsx`)**
- Added "Space Key" text input field to Confluence configuration form
- Field is optional (not required)
- Positioned after "Is Cloud" checkbox for logical grouping
- Added to initial values with empty string default

**2. Internationalization (`web/src/locales/*.ts`)**
- **English (`en.ts`)**: Added `confluenceSpaceKeyTip` with clear
instructions and examples
- **Chinese (`zh.ts`)**: Added Chinese translation for the tooltip
- **Russian (`ru.ts`)**: Added Russian translation for the tooltip
- **Bonus Fix**: Removed duplicate `deleteModal` object in `zh.ts` that
was causing TypeScript lint errors

### Backend Compatibility

No backend changes were needed! The `ConfluenceConnector` class already
supports the `space` parameter:

```python
def __init__(
    self,
    wiki_base: str,
    is_cloud: bool,
    space: str = "",  # ← Already supported!
    page_id: str = "",
    index_recursively: bool = False,
    cql_query: str | None = None,
    ...
)
```

The connector uses this parameter to filter the CQL query (line
1328-1330):
```python
elif space:
    uri_safe_space = quote(space)
    base_cql_page_query += f" and space='{uri_safe_space}'"
```

### User Experience

**Before:**
- Users could only sync ALL accessible spaces
- No UI option to limit scope

**After:**
- Users see "Space Key" field with helpful tooltip
- Tooltip explains:
  - Optional field (leave empty for all spaces)
  - Single space example: `DEV`
  - Multiple spaces example: `DEV,DOCS,HR`
- Available in English, Chinese, and Russian

### Future Enhancements

Potential improvements for future PRs:
- Add validation to check if space key exists before saving
- Add autocomplete/dropdown to show available spaces
- Add UI hints about space key format requirements
- Support for page_id filtering (already supported in backend)

---

## Related Issues

- Fixes #11638 - [Confluence] How to specify Space Key when adding
Confluence data source?

web/src/locales/ru.ts

@@ -711,6 +711,8 @@ export default {
         'Отметьте, если это экземпляр Confluence Cloud, снимите для Confluence Server/Data Center',
       confluenceWikiBaseUrlTip:
         'Базовый URL вашего экземпляра Confluence (например, https://your-domain.atlassian.net/wiki)',
+      confluenceSpaceKeyTip:
+        'Необязательно: Укажите ключ пространства для синхронизации только определенного пространства. Оставьте пустым для синхронизации всех доступных пространств. Для нескольких пространств разделите запятыми (например, DEV,DOCS,HR)',
       s3PrefixTip: `Укажите путь к папке в вашем S3 бакете для получения файлов. 
 Пример: general/v2/`,
       S3CompatibleEndpointUrlTip: `Требуется для S3 совместимого Storage Box. Укажите URL конечной точки, совместимой с S3.