chore(release): prepare 1.0.0-beta.6

[leoafarias]

Description

Prepare naked_ui 1.0.0-beta.6 for publication after the NakedTextField
selection-color fix merged in #77. This bumps the package version, adds a
curated changelog entry, and updates package metadata to the canonical
conceptadev/naked_ui repository.

The release tag must be created only after pub.dev automated publishing is
updated from btwld/naked_ui to conceptadev/naked_ui; the beta.5 publish run
failed because its OIDC repository did not match the configured repository.

Related Issues

None.

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Checklist

• Existing test coverage for the released fix is already on main; this
  PR changes release metadata only.
• The changelog and package metadata are updated; no API documentation
  changes are required.
• I am prepared to follow up on review comments in a timely manner.

Breaking Change

Does this PR require users of the package to manually update their code?

• Yes, this is a breaking change.
• No, this is not a breaking change.

Validation

• flutter analyze — passed with no issues.
• flutter test — all 662 tests passed; 3 external integration tests were
  intentionally skipped by default.
• flutter pub publish --dry-run — passed with 0 warnings.

[github-actions]

LCOV of commit 5c0add0 during Flutter CI #263

	(use "lcov --ignore-errors deprecated,deprecated ..." to suppress this warning)
Reading tracefile /tmp/__zgosalvez_github-actions-report-lcov/lcov.info.
Summary coverage rate:
  source files: 22
  lines.......: 89.6% (2944 of 3286 lines)
  functions...: no data found
  branches....: no data found
Message summary:
  1 warning message:
    deprecated: 1

Files changed coverage rate: n/a