fix: request every releases page once and cache release listings

[xepozz]

Problem

The release page loader built a new Paginator for every page:

$paginator = $this->api->getReleases(++$page);
$releases = $paginator->getPageItems();
// ...
$hasMorePages = $paginator->getNextPage() !== null;

getNextPage() performs the request for the next page, and the next iteration then built a fresh
paginator for that same page and requested it again. Every page but the first was fetched twice,
and each duplicate costs a GitHub or GitLab API rate limit unit.

Changes

• Every page is requested once. The loader keeps the paginator and asks it for the next page,
  because asking for the next page IS the request for it. Applies to both GitHubRepository and
  GitLabRepository.
• per_page=100. GitHub serves 30 releases per page by default and GitLab 20; both allow 100.
  A repository with 100 releases now costs one request instead of four (GitHub) or five (GitLab).
• Release listings can be cached between runs. A new ResponseCache wraps the listing request
  only — asset downloads share the same client and must never be written to the cache directory.
  Caching is off until cache-dir / DLOAD_CACHE_DIR is set; cache-ttl / DLOAD_CACHE_TTL
  defaults to 600 seconds and 0 disables it.

Only successful responses are stored, so a rate limit answer is not replayed after the limit is
gone. Entry age comes from the stored timestamp and not the file mtime, because a restored CI cache
writes the files with a fresh mtime and mtime-based entries would never expire. Entries are written
aside and renamed into place, so an interrupted or parallel run cannot leave a half-written file.
Any cache failure is logged and swallowed: the cache is an optimisation and must not turn a working
download into a failed one.

Tests

• GitHubRepositoryTest / GitLabRepositoryTest assert the exact pages requested ([1, 2, 3], not
  [1, 2, 2, 3, 3]), that pages stay lazy, that per_page=100 is sent, and that a second run with
  a carried-over cache directory sends no requests at all.
• FileResponseCacheTest covers the link header surviving the round trip (pagination depends on
  it), TTL expiry, mtime independence, unsuccessful responses not being stored, and corrupted
  entries being ignored.
• ResponseCacheBindingTest resolves the binding through a real bootstrap for the XML attribute,
  the environment variable, and the ttl=0 case.

composer test — 517 passed, 2 skipped. composer psalm — no errors. composer cs:diff — clean.

[codecov]

Codecov Report

❌ Patch coverage is 97.80220% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/Module/Cache/Internal/FileResponseCache.php	98.18%	1 Missing ⚠️
src/Module/Cache/Internal/NullResponseCache.php	50.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/Bootstrap.php	89.74% <100.00%> (ø)
src/Module/Cache/ResponseCache.php	0.00% <ø> (ø)
...e/Repository/Internal/GitHub/Api/RepositoryApi.php	52.45% <100.00%> (ø)
src/Module/Repository/Internal/GitHub/Factory.php	93.75% <100.00%> (ø)
...le/Repository/Internal/GitHub/GitHubRepository.php	57.14% <100.00%> (ø)
...e/Repository/Internal/GitLab/Api/RepositoryApi.php	51.61% <100.00%> (ø)
src/Module/Repository/Internal/GitLab/Factory.php	91.66% <100.00%> (-8.34%)	⬇️
...le/Repository/Internal/GitLab/GitLabRepository.php	55.88% <100.00%> (ø)
src/Module/Cache/Internal/FileResponseCache.php	96.42% <98.18%> (ø)
src/Module/Cache/Internal/NullResponseCache.php	33.33% <50.00%> (ø)

... and 60 files with indirect coverage changes

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