Fix search_model handling for dotted columns and query builders

[AbdelrhmanSaid]

Motivation

• Prevent runtime errors when search_model is called with a base QueryBuilder (non-Eloquent) or when dotted columns reference no relation on the model.
• Ensure the function return type matches the accepted input types to avoid type mismatches.
• Provide a safe fallback for dotted-column searches on non-Eloquent queries so search remains usable across different query types.

Description

• Updated search_model return type to Builder|QueryBuilder to match the accepted input signature in src/helpers.php.
• Changed the internal relation handler signature to accept Builder|QueryBuilder and added a void return type.
• When a dotted column is encountered, call orWhereHas only if the query is an Eloquent Builder and the relation method exists on the model; otherwise fall back to a plain orWhere on the column.
• Kept single-file change confined to src/helpers.php and preserved original behavior for non-dotted columns.

Testing

• Ran php -l src/helpers.php and it reported no syntax errors (success).
• Attempted ./vendor/bin/pint --test src/helpers.php but the pint tool is not installed in this environment (skipped).

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Codex Task