Add dedicated Graph config schema test

[Nice6042]

Closes #3735

Adds a dedicated Graph integration test that recursively compares the live Plotly config schema with the generated dcc.Graph config metadata. Known Plotly-internal paths remain excluded, and assertion messages identify the exact config path when the schemas drift.

Tests:

• python -m pytest components/dash-core-components/tests/integration/graph/test_graph_basics.py --headless -q — 14 passed, 1 skipped
• python -m black --check components/dash-core-components/tests/integration/graph/test_graph_basics.py — passed

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • add a dedicated Graph config-schema test
  • verify schema drift produces a path-specific failure
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

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