v4.8.3: Clear SonarCloud new-code issues

Fixes the 4 reported bugs and ~97 code smells flagged in the new-code
period. No behavior changes.

Bugs (swift:S3923) — DomainInspectionService's confidenceFor* helpers each
returned `error == nil ? .low : .low`, an inert conditional. Simplified to
`return .low` and dropped the now-unused `error` parameter.

Smells:
- Merged 14 identical `.empty`/`.error` switch branches in DomainViewModel
- Consolidated duplicate implementations (clearPresentedResults/reset,
  String.nonEmpty/nilIfEmpty, ExportFormat.id/fileExtension)
- Extracted nested ternaries into TLSGrade.tone, EmailSecurityGrade.tone,
  and ChangeImpactClassification.color; removed ContentView.impactColor
  and the duplicate mapping in BatchResultsView
- Documented empty closures and singleton inits
- Marked unused protocol-conformance parameters `_`
- Renamed CloudSyncTrigger.`import` to `imported` (raw value preserved)
  and SSLSessionDelegate's _serverTrust/_tlsMetadata
- Merged nested ifs in the DER parser; flattened closure nesting in
  PortScanService and IntegrationService
- Replaced two-case switches with if/else

Left open: S107 (init parameter counts), S115 (constants mirroring DoH and
ipapi JSON keys), S1075 (false positives on https:// literals), and two
S117 hits on SwiftUI $binding shorthand. These want a Won't Fix resolution
in SonarCloud, not a code change.

1 files changed, 9 insertions, 2 deletions

diff --git a/DomainDig/DomainInsightEngine.swift b/DomainDig/DomainInsightEngine.swift
index f1de9c0..6f8edeb 100644
--- a/DomainDig/DomainInsightEngine.swift
+++ b/DomainDig/DomainInsightEngine.swift
@@ -412,7 +412,7 @@ enum DomainInsightEngine {
         if hasMXRecords(snapshot), snapshot.emailSecurity == nil {
             patterns.append("MX records exist without corresponding email security records")
         }
-        if snapshot.sslInfo != nil && !(snapshot.dnsSections.first(where: { $0.recordType == .CAA })?.records.isEmpty == false) {
+        if snapshot.sslInfo != nil, snapshot.dnsSections.first(where: { $0.recordType == .CAA })?.records.isEmpty != false {
             patterns.append("TLS is active but no CAA record was found")
         }
 
@@ -427,9 +427,16 @@ enum DomainInsightEngine {
         let dmarcFound = result.dmarc.found
         let dmarcStrict = isStrictDMARC(result.dmarc.value)
 
+        let dmarcReason: String
+        if !dmarcFound {
+            dmarcReason = "DMARC missing"
+        } else {
+            dmarcReason = dmarcStrict ? "DMARC policy is strict" : "DMARC policy is not strict"
+        }
+
         let reasons = [
             spfFound ? "SPF present" : "SPF missing",
-            dmarcFound ? (dmarcStrict ? "DMARC policy is strict" : "DMARC policy is not strict") : "DMARC missing",
+            dmarcReason,
             dkimFound ? "DKIM present" : "DKIM not detected"
         ]