Add sACN input/output support and fix multi-source merging

- Add sACN/E1.31 protocol support for both input and output
- from_proto = "sacn" to receive from sACN multicast
- proto = "sacn" to output via sACN multicast
- Fix remap engine to maintain persistent state per output universe
- Multiple inputs targeting same output now merge correctly
- Prevents flickering when multiple universes feed same output

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

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

config.example.toml

@@ -19,6 +19,14 @@
 # To examples:
 #   "0.0.1"        - universe 1, starting at channel 1
 #   "0.0.1:50"     - universe 1, starting at channel 50
+#
+# Input protocol (optional, default "artnet"):
+#   from_proto = "artnet"  - receive via ArtNet
+#   from_proto = "sacn"    - receive via sACN/E1.31 (multicast)
+#
+# Output protocol (optional, default "artnet"):
+#   proto = "artnet"  - output via ArtNet (broadcast or discovered nodes)
+#   proto = "sacn"    - output via sACN/E1.31 (multicast)
 
 # Remap entire universe
 [[mapping]]
@@ -44,3 +52,15 @@ to = "0.0.7"
 [[mapping]]
 from = "0.0.3"
 to = "0.0.8"
+
+# Output to sACN instead of ArtNet
+[[mapping]]
+from = "0.0.4"
+to = 1
+proto = "sacn"
+
+# Convert sACN input to ArtNet output
+[[mapping]]
+from = 5
+from_proto = "sacn"
+to = "0.0.5"