refactor: update Accordion article to Aura theme

[sissbruecker]

Updates the Accordion page and examples to use the Aura theme.

Noteworthy changes:

• Simplified accordion summary example to only show an icon in the accordion heading once the continue button is clicked. The Aura styles do not stretch the heading content, thus the respective panel details were glued to the panel title and it would have required some CSS to make this work. IMO this works out fine, in general the example felt too complex and the Binder setup was also distracting.
• Updated accordion content example to have colored links with underline
• Removed small theme variant example as it isn't supported by Aura

[github-actions]

AI Language Review

AccordionContent.java:

• Ensure consistent use of color variables. The createStyledAnchor method sets the anchor text color to "var(--aura-blue-text)". Verify if this is the correct variable and if it matches the theme's color standards.

AccordionSummary.java:

• Ensure color variables like "var(--aura-green-text)" are defined and available in the theme for styling icons consistently.

accordion-styling.adoc:

• There are duplicate entries in the style variant descriptions, particularly for Filled Panels and Reverse Panels. Ensure that all entries are necessary and not repetitive, as this might confuse the reader.

AccordionExamples.ts:

• When using string interpolation for complex conditions or operations, such as in ${this.customerComplete ? '...' : '...'}, ensure clarity and simplicity, and consider abstraction for readability if it recurs.

For each of these points, ensure that the styling aspects align with the overarching theme/style guide of the application to maintain consistency in the UI/UX design.

[sissbruecker]

There probably should be a paragraph about how to apply style variants with a code snippet, especially since the terminology is now different from the theme attribute that you need to use. I think we can separately add a common section for this in a shared asciidoc and then include it in the styling pages that have a style variants section.

[web-padawan]

Could probably use {/* tag::snippet[] */} and {/* end::snippet[] */} in this example to not include the whole Accordion in the code example, but a single panel like in Lit version. Not a blocker though.

[web-padawan]

Could probably remove "since" tag from here as it was only relevant for V23 docs.

[jouni]

We should remove all [since] annotations from v25 docs (and any [since v23] annotations from v24 docs).

[web-padawan]

Let's probably align wording here with other variants below:

Suggested change

	|The filled theme variant makes the panel’s boundaries visible
	|Makes the panel’s boundaries visible

[web-padawan]

Let's use "style variant" consistently:

Suggested change

	The `filled` theme variant makes the panel's boundaries visible. This helps tie its content together visually and distinguishes it from the surrounding UI.
	The `filled` style variant makes the panel's boundaries visible. This helps tie its content together visually and distinguishes it from the surrounding UI.

[web-padawan]

Same as above, let's use "style variant" consistently:

Suggested change

	The `reverse` theme variant places the toggle icon after the summary contents. This can be useful for aligning visually the summary with other content.
	The `reverse` style variant places the toggle icon after the summary contents. This can be useful for aligning visually the summary with other content.