Add magic bytes deployment system for agent modes

- Agent config: Added EmbeddedConfig struct and RunMode enum for
  filename-based mode detection (Viewer, TempSupport, PermanentAgent)
- Agent main: Updated to detect run mode from filename or embedded config
- Server: Added /api/download/* endpoints for generating configured binaries
  - /api/download/viewer - Downloads GuruConnect-Viewer.exe
  - /api/download/support?code=123456 - Downloads GuruConnect-123456.exe
  - /api/download/agent?company=X&site=Y - Downloads with embedded config
- Dashboard: Updated Build tab with Quick Downloads and Permanent Agent Builder
- Included base agent binary in static/downloads

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/src/api/mod.rs

@@ -3,6 +3,7 @@
 pub mod auth;
 pub mod users;
 pub mod releases;
+pub mod downloads;
 
 use axum::{
     extract::{Path, State, Query},