[MaartenRimaux]

Summary

Documents asset parameters and macros on static assets (ADS-865, epic ADS-623).

• Ad targeting parameters guide: the backend section now covers static assets. It adds a static asset example with a macro, explains how the parameters end up on the resource URL (targeted URIs, static companions, only the HLS master playlist or DASH MPD request), and warns against using them on signed or tokenized URLs.
• New "In the dashboard" subsection: editing asset parameters, Copy as JSON, and Import parameters (JSON, query string or ad tag URL, with Merge or Replace).
• Breaks concept page: the static and VAST asset sections now mention assetParameters and link to the guide.
• VAST and vendor docs are unchanged apart from the cross-link. Precedence is still the existing "How the layers are merged" section, which applies to static assets as well.

Note: the dashboard subsection mentions editing parameters on static assets. This ships with ADS-637 (dashboard PR #197, merged into develop). Import/export (ADS-734) is already live.

Test plan

• prettier --check on the changed files
• mdxlint --frail (spellcheck) on the changed files
• Docusaurus build in CI (links and anchors)

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