Drop PHP 8.2, fix attribute/dot-notation resolution bugs, expand docs

[alexmerlin]

PHP support

• Require ~8.3.0 || ~8.4.0 || ~8.5.0 in composer.json and drop 8.2 from both CI matrices

Bugs

• Stop AttributedServiceFactory from treating a config value of null as a missing key (isset() → array_key_exists()/offsetExists())
• Throw instead of silently truncating a dot path that continues past a scalar
• Remove the mutable $originalKey property — shared factory instances make it stateful; pass the key as an argument
• Validate in AttributedRepositoryFactory that Doctrine returned the requested class, so an entity missing repositoryClass fails loudly
• Guard against an #[Entity] attribute naming a non-existent class
• Fix findEntityAttribute()/findInjectAttribute() returning object where ?Entity/?Inject is declared

Code quality

• Restrict attribute targets: #[Entity] to TARGET_CLASS, #[Inject] to TARGET_METHOD (misplacement is currently a silent no-op)
• Add InvalidArgumentException::missingKey() for parity with RuntimeException's static constructors
• Replace the hand-rolled attribute loops with getAttributes(X::class)
• Drop the ignoreErrors entries from phpstan.neon by fixing their cause in the tests

Tests

• Cover null config values, paths overshooting a scalar, dot notation on a non-array service, ArrayAccess traversal, exact-name precedence over dot resolution, unregistered class instantiation, missing entity, wrong repository class

Documentation

• Add an "Attributes vs. factories" page: comparison, advantages, trade-offs, when to still write a factory
• Add an FAQ page
• Correct the dot-notation description — only the full name and the first segment are resolved from the container, not every segment
• Document InvalidArgumentException, constructor-less classes, the unregistered-class fallback, ArrayAccess traversal, only-direct-recursion detection, the repositoryClass requirement, createObject() vs __invoke()
• Fix the unrunnable PHP samples (missing use statements) and the Srevice typos
• Update the README: requirements, QA section, un-pin the PHP badge from 1.3.0
• Reformat all Markdown to one sentence per row

Note: readKeysFromArray() gains a third parameter and the attribute-target change turns silent misuse into a compile-time error — backwardCompatibilityCheck will flag both.