feat(database): add labeled Tree/JSON switch for model data

[MadalenaBastakou]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the main branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx, where "xxx" is the issue number)

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

Models → Data already had a JSON renderer, but it was behind two unlabeled 24px icons that were easy to miss.

This change makes the switch first-class:

• Exclusive Tree / JSON ToggleButtonGroup with icons, labels, and tooltips
• Last view persisted in localStorage (conduit.schemaData.viewMode), default Tree
• JSON documents use the same outlined card chrome as the tree cards
• Per-document Copy JSON next to Edit/Delete
• Copy page copies the current page of documents as pretty-printed JSON
• Cancel in JSON edit restores the original document without flashing empty {}

Search, pagination, Refresh, Add Document, and per-document edit/delete still apply in both views.