[ui] Support Fluss UI for database and table management

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/fluss/issues) and found nothing similar.

### Motivation

Fluss currently provides APIs, SQL, CLI, and engine integrations for database and table operations, but users do not have an official UI for common metadata management and inspection workflows. For new users and operators, basic tasks still require SQL, CLI, or client code, which makes onboarding and day-to-day administration harder.

A lightweight Fluss UI would help users:

- Discover databases and tables in a cluster.
- Create databases and tables through guided forms.
- Inspect table metadata such as schema, primary key, partitioning, bucket count, table options, table id, and creation/update time if available.
- Quickly validate cluster and table state during development or operations.

### Solution

Introduce a Fluss UI module or deployable web application focused first on basic metadata management:

1. Cluster/database browser: list databases and tables.
2. Database management: create database and show database properties.
3. Table creation: support creating log tables and primary key tables with schema fields, primary key, partition keys, bucket number, and table options.
4. Table detail page: show schema, table type, primary key, partitioning, bucket number, table properties/options, and other available basic metadata.
5. Permission/safety: start with read-heavy views and explicit confirmation for create operations; destructive operations can be considered later.

The implementation can build on existing Admin/client APIs, adding lower-level APIs only where UI requirements expose missing metadata endpoints.

### Anything else?

This issue is intended to start a community discussion about the scope of an official Fluss UI. Advanced workflows such as altering tables, dropping resources, data preview/query, tiering status, metrics, and access control can be tracked separately after the basic metadata workflows are agreed.

### Willingness to contribute

- [x] I am willing to submit a PR!

Start by reviewing the existing Admin/client APIs and the proposed cluster, database, and table workflows. Agree the basic scope first; done means an official UI direction is settled for browsing metadata, creating databases and tables, and viewing table details, while advanced workflows remain separate.

Written by the indexing model from the issue text.