serve the web console from the node and drop the websocket bridge

The browser reached this node through `dora-websocket-transceiver`: a second
node, a second port, and a round trip through the dataflow for every button
press, to carry a UI only this node can interpret. The node now serves the
page and holds the browsers' sockets itself on one port, so the console is
one URL and a consumer wires nothing for it.

`dora_teleop/server.py` runs aiohttp on a thread of its own and meets the
control loop at two non-blocking points: a bounded queue the tick drains, and
a snapshot handed back. Both queues are bounded deliberately — a flood is
dropped rather than grown, and a slow browser loses stale snapshots rather
than the newest — because nothing a browser does may stall the thread that
stops the arm. A port already in use stops the node rather than leaving it
announcing a console nobody can open.

The web deadman moved but did not change: it was a `clients` message from the
bridge and is now the open-socket count read each tick. One hop fewer, same
meaning.

Contract, so 0.2.0 -> 0.3.0: `ui_command` and `clients` are gone. `ui_state`
stays published for `dora topic echo` and the bench, with no browser reading
it. New WEB_HOST and WEB_PORT (7000; 0 opens no port).

The console itself is laid out like the arm's own pendant — two rings
quartered into arc sectors you hold, each with its out-of-plane axis as pills
above. Directions and signs match xArm Studio on the controller, `Y+` on the
left included: two consoles driving one arm that disagree about which way is
+Y is a trap, not a preference.

Also sends a velocity only when it changes, repeating an unchanged one on
JOG_KEEPALIVE_S (0.2 s) purely to beat the consumer's own expiry. Repeating
every tick made `dora-ulite6` re-plan the same motion twenty times a second.
That turned out not to be the whole cause of the stepping an operator felt —
the rest was fixed in dora-ulite6 v0.3.1, pinned here — but sending 18
messages where 83 went before is worth keeping on its own.

`dora-joy` moves to v0.1.1: v0.1 is an annotated tag, and dora 1.0.1 records
the tag object's id as the commit hash and then rejects its own checkout for
sitting on the peeled commit. Neither dataflow could be built before this.

dataflow-gamepad.yml

@@ -27,7 +27,7 @@ debug:
 nodes:
   - id: joy
     git: https://gitea.liria.cl/liria/dora-joy.git
-    tag: v0.1
+    tag: v0.1.1
     build: pip install .
     path: dora-joy
     inputs:
@@ -47,7 +47,6 @@ nodes:
         source: joy/joy
         queue_size: 1
         queue_policy: drop_oldest
-      clients: bench/clients
       response: bench/response
       robot_state: bench/robot_state
       tcp_pose: bench/tcp_pose
@@ -61,6 +60,9 @@ nodes:
     env:
       SPEED_MM_S: "60"
       SPEED_DEG_S: "30"
+      # This one is about the pad, so the console stays shut. Set a port to
+      # bring it up alongside and watch the lease move between the two.
+      WEB_PORT: "0"
 
   # Declared, not spawned: `dora-teleop-probe` attaches to this id when you run
   # it, and the dataflow runs perfectly well when nobody does.
@@ -81,4 +83,3 @@ nodes:
       - robot_state
       - tcp_pose
       - joint_pose
-      - clients