Security: Deleted content exposure + revision history IDOR via sequential IDs

## Summary

Two information disclosure issues allow access to deleted/pending content:

### 1. Deleted Answer Content via GET /answer/api/v1/answer/info (Low-Medium)

\`AnswerService.Get()\` calls \`answerRepo.GetByID()\` which fetches answers by raw ID with no \`status != deleted\` filter. Deleted answers are returned with full content to unauthenticated callers.

**Secure comparison:** \`SearchList\` correctly filters: \`session.Where("status != ?", entity.AnswerStatusDeleted)\`

### 2. Revision History IDOR via GET /answer/api/v1/activity/timeline/detail (Medium)

\`GetObjectTimelineDetail\` fetches revision content by sequential integer ID (\`autoincr BIGINT\`). No check for whether the associated question/answer is deleted or pending. Any authenticated user can enumerate \`revision_id=1,2,3...\` to read full content of deleted/pending questions and answers.

**Secure comparison:** \`GetRevisionList\` correctly checks \`objInfo.IsDeleted()\` before showing history. \`GetQuestion\` blocks access to deleted/pending content.

### Impact

- Bypasses content moderation (admin-deleted content remains accessible)
- Reveals pending-review content before publication
- Sequential revision IDs make enumeration trivial

## Discovery

Found through automated security research comparing content visibility controls across endpoints.

Inizia con AnswerService.Get e GetObjectTimelineDetail per i due endpoint interessati, quindi confronta i relativi controlli di accesso con SearchList, GetRevisionList e GetQuestion. Traccia il modo in cui vengono caricate le domande, le risposte e le revisioni eliminate e in sospeso. Il lavoro è completato quando le risposte eliminate non sono più esposte agli utenti non autenticati e il contenuto delle revisioni eliminate o in sospeso non è più esposto agli utenti autenticati, mentre il contenuto consentito rimane accessibile.

Scritto dal modello di indicizzazione a partire dal testo della issue.