feat: audio transcription, built-in skills, office export engines, and answer style controls

1. Audio & Media Transcription Pipeline

Database & Storage: Added backend/migrations/60_document_transcripts.sql creating the document_transcripts table for persisted transcripts and segments.
Worker Pipeline: Integrated asynchronous transcription jobs with Whisper language detection (whisperLanguage.ts), transcript polishing (transcriptPolish.ts), and usability quality gates (transcriptQuality.ts).
Frontend Media Experience:
- Added
  
  MediaView.tsx with audio playback, synchronized transcript follow-along (
  
  SyncedTranscript.tsx), and language chooser.
- Added attachment tile state handling (
  
  AttachmentTile.tsx) in prompt inputs with real-time transcription status.

2. Inlined Built-in Agent Skills

Inlined 27 domain-specific skills into the backend esbuild bundle via build.mjs (NDA triage, cease & desist, policy diffing, diligence issue extraction, vendor agreements, trademark clearance, etc.).
Introduced

skillTools.ts and tool whitelisting for agent runs.

3. Office Deliverables & Artifact Export Engines

Enhanced presentation and spreadsheet generators (

exportPptx.ts,

exportXlsx.ts) with theme styling, metric callouts, and clean formatting.
Upgraded HTML artifact viewer (

exportHtmlArtifact.ts) and DOCX export with watermark support.

4. Answer Style & Depth Precedence

User Instruction Precedence: Added WHAT THE USER ASKS FOR WINS rule over default answer templates in

definitions.ts.
Style Control: Added answerStyle parameter (auto | concise | detailed) on POST /agents/chat with dynamic system prompt injection and analytics tracking.

5. Trial Gating & Account Deletion Ledger

6. Library & Navigation Updates

Unified case search into

/app/library and preserved query parameters with a backward-compatible redirect stub on /app/cases.
Updated desktop sidebar and mobile drawer navigation.

7. Brand Assets & Marketing Pages

Added modern application favicons and apple-touch icons (favicon-*.png, icon-*.png).
Added webp assets for role landing pages (Employment, In-House, Tax).
Refreshed SEO metadata, sitemap.ts, and llms.txt.