Make plotly-cloud a default install dependency

[T4rk1n]

Summary

Makes plotly-cloud a default install dependency of Dash instead of only being available through the optional dash[cloud] extra. plotly-cloud (imported as plotly_cloud) powers the plotly console entry point and Dash's cloud integration in dash/dash.py, so shipping it by default means those features work out of the box.

Changes

• Add plotly-cloud to requirements/install.txt (unpinned, matching the file's existing style and requirements/cloud.txt).
• Keep the cloud extra (requirements/cloud.txt + setup.py extras_require) unchanged so pip install dash[cloud] still resolves for backward compatibility. It is now redundant but non-breaking.
• Update the ImportError hint in dash/_plotly_cli.py: since plotly-cloud is now always installed, the stale dash[cloud] suggestion is replaced with pip install plotly-cloud (or reinstalling dash). The defensive try/except is retained.
• Add a CHANGELOG entry under Added.

Closes #3513

[ndrezn]

The [cloud] shortcut should also be removed right? Or are you worried about backwards compatibility?

[T4rk1n]

The [cloud] shortcut should also be removed right? Or are you worried about backwards compatibility?

Yes, can keep it for backward compatibility until next major release.

[camdecoster]

Any idea why the tests still aren't passing?

[T4rk1n]

@camdecoster The ci is now fixed, there was an issue with id added that the tests were not built for.

[camdecoster]

Looks good. Just need to address the CHANGELOG merge conflict.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Dash performance benchmarks

✅ all within thresholds

	scenario	metric	p90 (ms)	median	growth	baseline p90	note
✅	callback_chain	chain_ms	475.9	459.4	0.94x	499.1
✅	callback_chain	graph_ms	2.1	2.1	1.0x	2.4
✅	callback_fanout	fanout_ms	91.6	81.5	0.83x	92.5
✅	deep_nesting	render_ms	64.1	56.2	1.12x	56.8
✅	full_children_replace	replace_ms	5359.5	2376.7	18.75x	4697.1
✅	initial_render_large	render_ms	600.7	540.2	0.89x	694.4
✅	initial_render_small	render_ms	108.9	101.0	0.77x	104.0
✅	patch_append_nested	append_ms	190.5	141.3	3.04x	192.3
✅	patch_append_toplevel	append_ms	156.7	93.6	2.95x	140.2
✅	patch_scalar_update_large	update_ms	212.9	193.0	0.92x	202.9
✅	wildcard_all_resolve	wildcard_ms	354.2	318.7	0.86x	313.6
✅	wildcard_all_resolve	graph_ms	1.6	1.6	1.0x	1.3

growth = late-third / early-third per-op time; ~1 is flat, a large value means the per-op cost scales with accumulated state.

machine scale vs baseline: 1.05x - divided out of the baseline ratios so they compare like for like (the absolute warn/fail ceilings are left un-scaled); calibrated on initial_render_small.