docs: add the cursor and recolouring recipes and sharpen four pages

[Gamote]

What

• Follow the cursor, a new recipe in the interactions gallery: the pointer's horizontal position sets the frame through seek({ percent }), leaving rewinds. The migration guide's mode: "cursor" row now points at it, and "Writing your own" lists cursor among the plain-handler recipes.
• Recolouring, a new section on the styling page with a live example (fill and stroke to currentColor on the animation's element, since artwork draws with either or both) and one sentence on recolouring the data itself for every renderer; the Basics gallery reuses the example.
• The custom-factory example read a copy of context.lottie taken at attach time, so on a prerendered page its root stayed null and the "play while pressed" behaviour never armed (it worked after a client-side navigation only because the root happened to be there already). It now reads the context on every use, the page says why, and the JSDoc of LottieInteractionContext.lottie carries the same note.
• Installation: where <Lottie> goes under React Server Components (a "use client" file, which still renders on the server). The instance page: the reported frame counts from the start of the playable range.

Verified

• Website check green (examples typecheck, 35 pages prerendered, assert-rendered clean); Biome clean.
• On the built site in a real browser: the cursor example follows the pointer and rewinds on leave; the recolour example's three paths (two gradient strokes, one gradient fill) all compute to the text colour; the custom-factory example now registers its listener and plays on a direct load.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.91%. Comparing base (f44617b) to head (b652104).

Additional details and impacted files

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##             main     #135   +/-   ##
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  Coverage   99.91%   99.91%           
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  Files          47       47           
  Lines        1223     1223           
  Branches      361      361           
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  Hits         1222     1222           
  Misses          1        1           

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