feat(dashboard): add polished Fortal dashboard example

[leoafarias]

Description

• Adds a workspace-only, non-published Fortal dashboard example for macOS and web, covering overview, customers, orders, settings, and the component gallery.
• Demonstrates responsive navigation, data-grid interactions, account and row-action popovers, live theme controls, and representative Fortal component states.
• Uses the finalized APIs from feat(fortal): align visuals with Radix Themes 3.3.0 #80, including RemixRadioGroup composition around FortalRadio.
• Keeps the change isolated to packages/dashboard/** plus the root workspace registration. It does not modify Remix library code, demos, tools, generated files, dependencies, or the lockfile.

Related Issues

Related to #80. Host-agnostic shell and overlay follow-up: #82.

Visual Evidence

Desktop — 1440 × 900

Compact — 390 × 844

Validation

• fvm dart run melos run ci — passed: hosted Mix consumer resolution, clean generation, documentation validation, Fortal parity, 17 dashboard tests, and 2,109 Remix tests.
• cd packages/dashboard && fvm flutter analyze — passed with no issues.
• cd packages/dashboard && fvm flutter test — all 17 tests passed.
• cd packages/dashboard && fvm flutter build web — passed.
• cd packages/dashboard && fvm flutter build macos --debug — passed.
• git diff --check origin/main...HEAD — passed.
• Diff audit — limited to packages/dashboard/** and the root pubspec.yaml workspace entry.

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Checklist

• My PR includes unit or integration tests for all changed/updated/fixed behaviors.
• I have updated or added relevant documentation (doc comments with ///).
• 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.