This commit bumps the TypeScript version to latest 5.3.
It also introduces `verbatimModuleSyntax` configuration, a feature of
TypeScript 5. This enables the restriction for import statements that
`import type` must be used if the imported thing is used as a type only
(and not used as a value). Such imports will get fully erased when
TypeScript compiles the sources to JavaScript. Also it can help tools
like bundlers to determine whether an import is needed at runtime or not.

- Replace deprecated "import assertions" syntax with "import
  attributes".
  ESLint supports it (typescript-eslint/typescript-eslint#7719).
- Enable `verbatimModuleSyntax` improved in 5.3, refactor the code to
  use type-only imports.
  Its usage is endorsed by offical Vue guide (vuejs/docs#2592).

This commit bumps the TypeScript version to latest 5.3.
It also introduces `verbatimModuleSyntax` configuration, a feature of
TypeScript 5, endorsed by offical Vue guide (vuejs/docs#2592).

This enables the restriction for import statements that
`import type` must be used if the imported thing is used as a type only
(and not used as a value). Such imports will get fully erased when
TypeScript compiles the sources to JavaScript. Also it can help tools
like bundlers to determine whether an import is needed at runtime or not.

- Replace deprecated "import assertions" syntax with "import
  attributes".
  ESLint supports it (typescript-eslint/typescript-eslint#7719).

This commit upgrades TypeScript to the latest version 5.3 and introduces
`verbatimModuleSyntax` in line with the official Vue guide
recommendatinos (vuejs/docs#2592).

By enforcing `import type` for type-only imports, this commit improves
code clarity and supports tooling optimization, ensuring imports are
only bundled when necessary for runtime.

Changes:

- Bump TypeScript to 5.3.3 across the project.
- Adjust import statements to utilize `import type` where applicable,
  promoting cleaner and more efficient code.