dotbot: drop the classic web UI, the console is the only one

[geonnave]

Removes the classic web UI, the React app in dotbot/frontend/ served at /PyDotBot. The console at /console has covered what the fleet is driven with (map, joystick, waypoints, swarmit orchestration) for a while, and carrying two React apps doubled the frontend CI, the packaging hooks and every UI-facing change to the controller.

What goes: the whole dotbot/frontend/ tree, about 22k lines of which 16.9k are its package-lock.json, plus its wiring: the /PyDotBot static mount and the PYDOTBOT_FRONTEND_BASE_URL constant in dotbot/server.py, the sdist hook's frontend build, the wheel-contents check's frontend entry, the CI frontend job, the frontend step of tox -e web, and the frontend codecov flag.

What replaces it: the console, unchanged. / now redirects to /console/, but only when the console is built; without the build neither route exists and the controller logs that it is serving the API alone. dotbot run controller opens the console, or nothing when it is not built.

What is retired with it, each with a follow-up tracked:

• The qrkey phone page. dotbot run demo qr still relays the controller's notifications to MQTT and shows the QR, and --webbrowser now opens the QR's own URL, but no phone page reads the relay until the console grows a qrkey mode.
• The SailBot and XGO views.
• The REST demo page.

This is a breaking change for anyone with /PyDotBot bookmarked; it now answers 404. The CHANGELOG says so.

It is split out of #304 and lands before it, so #304 no longer carries the removal and does not have to migrate the classic UI to its new stream.

Validated locally: full pytest (the only failures are machine-local, four config-path tests reading a real ~/.dotbot/config.toml and one simulator test whose port is taken), console build, lint and vitest (636 tests), a wheel built with hatch build passing utils/check_wheel_contents.py with no dotbot/frontend entries, and pre-commit run --all-files.

	Lines	Files
Classic UI lockfile (dotbot/frontend/package-lock.json)	-16907	1
Classic UI tests	-2642	18
Classic UI source and config	-2811	32
Server, tests, packaging, CI, docs	+116 / -167	20
Total	+116 / -22527	71

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.38%. Comparing base (15bd999) to head (0c5c1b4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #306      +/-   ##
==========================================
- Coverage   86.11%   84.38%   -1.74%     
==========================================
  Files         210      178      -32     
  Lines       27920    24251    -3669     
  Branches     2126     1569     -557     
==========================================
- Hits        24044    20463    -3581     
+ Misses       3868     3784      -84     
+ Partials        8        4       -4     

Flag	Coverage Δ
console	79.35% <ø> (ø)
frontend	?
python	87.25% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
dotbot/cli/_lazygroup.py	92.30% <ø> (ø)
dotbot/examples/qrkey_demo/client.py	48.33% <ø> (ø)
dotbot/server.py	93.96% <100.00%> (+0.37%)	⬆️
dotbot/tests/test_cli_dispatcher.py	100.00% <ø> (+0.88%)	⬆️
dotbot/tests/test_server.py	100.00% <100.00%> (ø)

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