fix(router): opt in to React Router v7 future flags

[pedrokohler]

Context

Opt in to React Router v7 future flags.

Benefits

• Removes noisy console warnings.
• Exercises v7 semantics early.
• Low-risk prep for a smoother v7 upgrade if we choose to do it later.
• No functional changes.

Changes & Results

Before:

After:
No warnings.

Testing

Checklist

PR

• [] My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• [] My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• [] OS:
• [] Node version:
• [] Browser:

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