feat: default http client timeout to 30s

[turegjorup]

Summary

The bundle exposes http_client_options (timeout, proxy, verify) but applied no defaults. An omitted timeout fell through to Guzzle's default of 0 — wait indefinitely — so a slow or hung identity provider could block a worker process forever. This PR adds a sensible default for the one option where it matters.

Features Added

• http_client_options.timeout now defaults to 30 seconds when unset, bounding how long an IdP call can block a worker.
• addDefaultsIfNotSet() on the http_client_options block so the default still materializes when the block is omitted entirely (the manager merges it via +=).
• proxy (no sensible default) and verify (Guzzle already defaults to secure true) are deliberately left unset.

Files Changed

• src/DependencyInjection/Configuration.php - Add addDefaultsIfNotSet() and defaultValue(30.0) on timeout.
• tests/DependencyInjection/ConfigurationTest.php - Replace testHttpClientOptionsAbsentByDefault with testHttpClientOptionsDefaultsApplied, asserting the default applies while proxy/verify stay absent.
• README.md - Document the new default and the timeout: 0 opt-out.
• CHANGELOG.md - Add entry under [Unreleased].

Test Plan

• task test — full suite passes (79 tests).
• task analyze:php — PHPStan clean at max level.
• Configure a provider with no http_client_options; confirm the Guzzle client receives timeout = 30.0.
• Set timeout: 0 on a provider; confirm Guzzle reverts to wait-indefinitely behaviour.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (af57823) to head (8294541).

Additional details and impacted files

@@             Coverage Diff             @@
##             develop       #42   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity        62        62           
===========================================
  Files              9         9           
  Lines            280       282    +2     
===========================================
+ Hits             280       282    +2     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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