Fix SSE real-time streaming in Home Assistant Ingress mode

Add padding to overcome aiohttp 64KB buffer in HA Supervisor.

Problem:
- HA Supervisor uses aiohttp with 64KB StreamResponse buffer
- Small SSE events (~200-500 bytes) were buffered until connection closed
- Users saw all streams appear at once instead of real-time updates

Solution:
- Detect Ingress mode via X-Ingress-Path header
- Add 64KB SSE comment padding to fill proxy buffers
- Increase progress interval to 3 sec in Ingress mode (reduce traffic)
- Normal mode (Docker/direct) unchanged - works exactly as before

Traffic impact:
- Normal mode: ~17KB per scan (unchanged)
- Ingress mode: ~2-3MB per scan (acceptable for real-time updates)

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

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

internal/camera/discovery/scanner.go

@@ -411,7 +411,14 @@ func (s *Scanner) testStreamsConcurrently(ctx context.Context, streams []models.
 	defer cancelProgress()
 
 	go func() {
-		ticker := time.NewTicker(1 * time.Second)
+		// Use longer interval for Ingress mode to reduce traffic (padding is ~64KB per event)
+		// Normal mode: 1 second, Ingress mode: 3 seconds
+		progressInterval := 1 * time.Second
+		if streamWriter.IsIngress() {
+			progressInterval = 3 * time.Second
+		}
+
+		ticker := time.NewTicker(progressInterval)
 		defer ticker.Stop()
 
 		for {
@@ -419,7 +426,7 @@ func (s *Scanner) testStreamsConcurrently(ctx context.Context, streams []models.
 			case <-progressCtx.Done():
 				return
 			case <-ticker.C:
-				// Send progress every second to prevent WriteTimeout
+				// Send progress to prevent WriteTimeout and show scanning activity
 				_ = streamWriter.SendJSON("progress", models.ProgressMessage{
 					Tested:    int(atomic.LoadInt32(&tested)),
 					Found:     int(atomic.LoadInt32(&found)),