Serve the site's fixed logos through NgOptimizedImage

[adamjohnwright]

Part of #338: the "static logos" step its plan starts with.

• ngSrc with intrinsic width/height on the navigation-bar logo (light and dark), the home-page logo, the four sponsor logos and the three related-project logos. The sizes were read from the files.
• The header logo is marked priority: it's the likely LCP element on every page, so it gets fetched eagerly with high priority. Both variants are marked, because which one shows depends on the theme.
• The home page's lower logos now load lazily, the directive's default.

A layout trap, measured

The sponsor logos were sized by max-width: 80px; max-height: 50px alone. With the width/height attributes that ngSrc requires, the browser stretched every one to 80×50. .sponsor-logo now also sets width: auto; height: auto, so the attributes only give the browser each logo's shape early.

How it was checked: every logo's rendered box was recorded on beta (main) and on this branch, served locally, at 1400px and 390px wide in light and dark:

• with the CSS fix: 36 of 36 identical, all loaded;
• without it: 16 differ, all sponsor logos at 80×50.

Review notes

• Development builds now warn (NG02960) about four oversized images. The 2126px header logo is drawn at about 215×45 on every page, plus the home logo and the NYU and OHSU sponsor logos. These are warnings, not errors; production builds don't check. They're a fair hint: smaller copies of those files (2× their drawn size) would save most of each download. That's an asset change for a follow-up.
• Both header logos are priority, so the hidden theme's copy (about 37KB) is fetched at high priority. It was always fetched, eagerly, before; which copy shows isn't known until the theme is.
• No SSR or prerender, so priority adds no <link rel=preload>. The default loader leaves src as the same relative assets/… path, so nothing changes under /curatorgraph/ either.

Left for the rest of #338

The images whose size isn't known in advance (pathway figures, the diagram thumbnail, EHLD legend items, partner logos, article images, icons) need the per-image fill-in-a-sized-container decision #338 describes. prefer-ngsrc stays off until then.

Tests

• Build and types: npm run build and check:types pass.
• e2e: homepage, home-stats, content-pages and back-button: 45 passed. The fixture fails on any Angular dev-mode error.
• Gates: check:lint and check:dead unchanged at their baselines.

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