feat: paste detection in chat — collapsible code attachments

[ShaerWare]

Summary

• Paste detection: when pasting large text (≥5 lines or ≥500 chars) into chat textarea, it's intercepted and shown as a removable chip with auto-detected language (~17 languages: Python, TS, JS, PHP, Go, Rust, SQL, etc.)
• Fenced code blocks on send: pasted blocks are wrapped as ```lang ... ``` in message content — no backend changes needed
• Collapsible code blocks: user messages containing code blocks render with 200px max-height and gradient fade, click to expand
• Admin + Mobile: identical pasteDetect utility in both apps, chips UI themed for each (admin: primary colors, mobile: night-eyes amber/stone)
• Mobile message actions: edit, summarize branch, regenerate, delete — wired up to existing API endpoints
• Mobile chat API: added editMessage, summarizeBranch, regenerateResponse methods
• Systemd service: updated to use start_gpu.sh with proper kill/timeout signals
• i18n: pastedLines + removePasted keys in ru/en/kk

NEWS

📎 Умная вставка кода в чат

Теперь при вставке большого текста (код, логи, конфиги) в чат — он
автоматически определяется как вложение с языком программирования
(Python, TypeScript, SQL и ещё ~15 языков). Вложение отображается
как компактный чип, который можно удалить до отправки. В истории
чата код показывается в сворачиваемом блоке — как в Claude.ai.
Работает и в админке, и в мобильном приложении.

Test plan

• Admin chat: paste a Python snippet (>5 lines) → appears as chip with "Python" label, not in textarea
• Admin chat: send with only paste, no typed text → message sent with fenced code block
• Admin chat: paste small text (<5 lines) → normal paste behavior
• Admin chat: multiple pastes → multiple chips, each removable
• Admin chat: code block in user message → collapsible with gradient, click to expand
• Admin CC mode: same paste behavior works
• Mobile: paste large text → chip appears above textarea
• Mobile: user message with code block renders with markdown
• Mobile: message action buttons (edit, summarize, regenerate, delete) work
• Build: cd admin && npm run build ✅
• Build: cd mobile && npm run build ✅

🤖 Generated with Claude Code