refactor(eslint): add sort-lit-element-members rule

[Galimede]

Context

LitElement components in this codebase follow a conventional member ordering defined in docs/cc-example-component.js:
properties → static members → constructor → public methods → private methods → event handlers → lifecycle → render → sub-render → styles.

This ordering was not enforced, and several components had members out of order.

What does this PR do?

• Adds an ESLint custom rule (lit-cc/sort-element-members) that enforces the conventional member ordering with autofix,
• Detects LitElement classes via extends LitElement or the presence of static get properties() / static get styles(),
• Reports on each out-of-order member individually with a descriptive message,
• Adds @types/estree as a dev dependency for proper typing,
• Applies the autofix across the codebase (45 files, pure reordering).

How to review?

• Check the commits,
• npm run test:mocha -- --grep "sort-lit-element-members" — 13 tests pass,
• 2 reviewers should be enough.

[github-actions]

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