fix: add template validation for sablon 0.4.3 compatibility

Sablon 0.4.3 no longer raises Zip::Error for nonexistent template files,
instead returning an empty ZIP. This breaks the error handling in
CaseCourtReportsController that relies on catching Zip::Error to show
users a friendly "Template is not found" message.

Changes:
- Add file existence validation in CaseCourtReport#initialize
- Raise Zip::Error with descriptive message if template doesn't exist
- Update test to expect error during initialization (fail-fast approach)
- Maintain backward compatibility with existing error handling

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: compwron

app/models/case_court_report.rb

@@ -7,6 +7,8 @@ class CaseCourtReport
 
   def initialize(path_to_template:, context:)
     @context = context
+    # Validate template exists before processing (sablon 0.4+ no longer raises Zip::Error)
+    raise Zip::Error, "Template file not found: #{path_to_template}" unless File.exist?(path_to_template)
     # NOTE: this is what is used for docx templates
     @template = Sablon.template(path_to_template)
   end

spec/models/case_court_report_spec.rb

@@ -393,8 +393,9 @@
           path_to_template: nonexistent_path
         }
         context = CaseCourtReportContext.new(args).context
-        bad_report = CaseCourtReport.new(path_to_template: nonexistent_path, context: context)
-        expect { bad_report.generate_to_string }.to raise_error(Zip::Error)
+        expect {
+          CaseCourtReport.new(path_to_template: nonexistent_path, context: context)
+        }.to raise_error(Zip::Error, /Template file not found/)
       end
     end