fix(docker): UDP relay for multi-source ESP32 on Docker Desktop Windows (#502)

Docker Desktop on Windows demultiplexes inbound UDP from multiple source
IPs onto a single virtual socket, silently dropping packets from all but
one ESP32 node. This makes multi-node sensing setups appear to work
(WebSocket connects, packets flow on the host) while only one node's CSI
ever reaches the container.

Adds scripts/udp-relay.py (stdlib only) which collapses multi-source UDP
to a single loopback source so Docker's forwarding accepts every packet.
Verified locally: 6 packets from 3 distinct source ports all arrive at
the receiver from a single relay socket.

Updates docker/docker-compose.yml with an inline comment pointing
Windows users at the relay + 5006:5005 mapping. Linux/macOS hosts are
unaffected and need no changes.

Also documents the workaround alongside fixes for #188 (UI 404 from
relative --ui-path) and #438 (boot loop on --edge-tier 1/2 against
pre-v0.4.3.1 firmware) as new sections 9-11 of docs/TROUBLESHOOTING.md.
Supersedes the docs-only PR #413.

Closes #374, #386
Refs #188, #438, #301

docker/docker-compose.yml

@@ -9,7 +9,18 @@ services:
     ports:
       - "3000:3000"   # REST API
       - "3001:3001"   # WebSocket
-      - "5005:5005/udp"  # ESP32 UDP
+      # ESP32 UDP. On Linux/macOS this works with multiple ESP32 nodes out of
+      # the box. On Docker Desktop for Windows, multi-source UDP is collapsed
+      # to one source IP at the WSL/Hyper-V boundary, so all-but-one node's
+      # frames are silently dropped (issue #374, #386).
+      #
+      # Windows workaround: change this to "5006:5005/udp" and run the host
+      # relay so every datagram arrives from the same loopback source:
+      #
+      #   python scripts/udp-relay.py --listen-port 5005 --forward-port 5006
+      #
+      # See docs/TROUBLESHOOTING.md §9 for details.
+      - "5005:5005/udp"
     environment:
       - RUST_LOG=info
       # CSI_SOURCE controls the data source for the sensing server.