fix(components): add missing user validation in ComponentHandler

[mahmoud-40]

Adds missing user validation to methods in ComponentHandler.java that accepted a User parameter without validating it before delegating to the database handler layer, allowing null or malformed users to propagate silently into the database handler.

• Fixes Missing user validation in several ComponentHandler methods #3971
• No new dependencies added.

Suggest Reviewer

@GMishx @amritkv @rudra-superrr @bibhuti230185

How To Test?

The fix is a defensive validation addition with no business logic changes. To verify:

1. Confirm that calling any of the affected methods with a null User now fails fast with a clear validation error rather than propagating into the handler layer.
2. Run the existing component-related unit tests; no changes to expected behavior, all existing tests should pass as-is.

Affected methods:

• Added assertUser(user): getRecentReleasesWithAccessibility, getReleaseIdsFromComponentId, getAccessibleReleasesFromVendorIds, getUsingComponentsWithAccessibilityForRelease, getUsingComponentsWithAccessibilityForComponent, getRecentComponentsSummaryWithPagination, refineSearchWithAccessibility, getAccessibleRecentComponentsSummary, searchAccessibleReleases
• Added null-safe guard returning Collections.emptyMap(): refineSearchAccessibleComponents, searchComponentByNamePrefixPaginated, searchComponentByExactNamePaginated these declare no throws clause so assertUser cannot be used directly.

No additional tests implemented; the change is purely defensive input validation consistent with the existing pattern throughout the class.

Checklist

Must:

• All related issues are referenced in commit messages and in PR