Refactor: Reduce PHPStan baseline by fixing suppressed type errors in src/

[rachana192837]

Summary

The phpstan-baseline.neon currently suppresses a number of pre-existing
PHPStan errors to allow CI to pass on legacy code. Some of these ignored
errors are fixable with small, safe refactors — such as adding missing return
types, fixing nullable type hints, or removing unreachable code — without
changing any behaviour.

Goal

Reduce the number of ignored errors in phpstan-baseline.neon by addressing
a targeted subset in src/, with no functional changes.

Motivation

• Improves long-term type safety and IDE support across the codebase
• Aligns with the project's clean code & TDD culture
• Makes future PHPStan level upgrades easier
• Low risk: purely additive type annotations or small structural fixes

Proposed Scope

Focus on one category of baseline errors per PR, for example:

• Missing return type declarations on public/protected methods
• Nullable parameter types that can be made explicit (?Type hints)
• Dead else branches after early returns

Each PR removes the corresponding entries from phpstan-baseline.neon and
confirms CI stays green.

References

• phpstan-baseline.neon
• phpstan.neon
• .github/onboarding.md

[silvinhamds2-arch]

IA