[IT9PE1-30742] Add ItalianFiscalCode constraint, validator and provider

[fguimier]

What

Add the ItalianFiscalCode constraint — the 11-digit numeric Codice Fiscale of Italian legal persons, which shares its format and Luhn check digit with the Partita IVA — following the FrenchSiret Luhn-delegation pattern:

• ItalianFiscalCode extends Symfony's Luhn (#[HasNamedArguments], default message); ItalianFiscalCodeValidator extends LuhnValidator: format failure (^\d{11}$) → own WRONG_FORMAT_ERROR, checksum failure → inherited Luhn::CHECKSUM_FAILED_ERROR.
• The 16-character personal codice fiscale is rejected: organization identifiers only (documented in the validator docblock).
• ItalianFiscalCodeProvider: maps the italianFiscalCode DBAL type (doctrine-types-bundle v2.18.0) to the constraint — autoconfigured, no DI change.
• README: new validator entry.

Refs IT9PE1-30742

Test plan

• ItalianFiscalCodeValidatorTest (shared ConstraintValidatorTestCase): 3 real Luhn-valid values (Adyen docs example + two public identifiers), 6 format-invalid cases (incl. the 16-char personal codice fiscale) and 1 checksum-invalid case asserting Luhn::CHECKSUM_FAILED_ERROR.
• ItalianFiscalCodeProviderTest: italianFiscalCode type → [new ItalianFiscalCode()].
• vendor/bin/phpcs, vendor/bin/phpstan, vendor/bin/phpunit (332 tests) green in the open-source container, with doctrine-types-bundle v2.18.0 resolved from Packagist.

Shipping

Merging this PR ships nothing: it needs a semver tag / GitHub release (v2.49.0, covering the DutchKvkNumber PR #96 too), then a
composer require assoconnect/validator-bundle:^2.49 bump PR in the backend. Two reviews total.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

❌ The last analysis has failed.

See analysis details on SonarQube Cloud

[fguimier]

🤖 Review gate — 0 error / 1 warning / 1 info

Human review needed: no — mechanical pattern copy of an established sibling (FrenchSiret Luhn delegation); the single warning is non-behavioral; can be merged without a peer review.

⚠️ Warnings (1) — non-blocking, see the fix offer in the session:

• tests/Validator/Constraints/ItalianFiscalCodeValidatorTest.php:31 — Fixture-provenance comments added in the test are change-rationale; move to the PR description or the yield keys.

📋 Card audit: 6 done

⚠️ Self-review by the author is mandatory before merging, regardless of this verdict.