Add multi-authentication support and comprehensive stream discovery

Major improvements to camera stream discovery system:

**Multi-Authentication Support:**
- Implement smart authentication fallback chain for HTTP/MJPEG/JPEG streams
- Add combined authentication method (Basic Auth header + query params) - fixes ZOSI cameras
- Support for: No Auth, Basic Auth, Query Params, Combined, Digest
- Auto-detect authentication method from URL and try appropriate chain

**Protocol & Detection Enhancements:**
- Add HLS (.m3u8) stream detection
- Add MPEG-DASH (.mpd) stream detection
- Add WebSocket stream detection
- Improve JPEG detection by URL extension when Content-Type is incorrect
- Add AuthMethod field to DiscoveredStream model

**Bug Fixes:**
- Fix port 0 bug: use default ports (HTTP=80, HTTPS=443, RTSP=554) when entry.Port==0
- Ensure URLs are built with correct ports from database or defaults

**Debug & Logging:**
- Add comprehensive DEBUG logging to builder.go (URL generation)
- Add comprehensive DEBUG logging to tester.go (stream testing & auth)
- Add comprehensive DEBUG logging to scanner.go (URL collection & deduplication)
- Log auth method detection, chain determination, and test results

**Results:**
- Tested with ZOSI ZG23213M camera: 4 streams found (was 0)
- Combined auth method successfully detects streams requiring both header + params
- Better coverage for cameras with non-standard authentication requirements

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

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

pkg/sse/sse.go

@@ -334,5 +334,10 @@ func (sw *StreamWriter) SendProgress(current, total int, message string) error {
 
 // Close closes the stream writer
 func (sw *StreamWriter) Close() {
+	// Perform final flush if possible
+	if flusher, ok := sw.client.Response.(http.Flusher); ok {
+		flusher.Flush()
+	}
+
 	sw.client.Cancel()
 }