feat(templates): Add processing issues data types

Add ProcessingIssueData and IssueStats types to templates/types.go for use
in the processing issues management UI. These types support:

- ProcessingIssueData: Individual issue details including ID, media item,
  file path, format, issue type, severity, and timestamps

- IssueStats: Aggregated counts of issues by severity (error, warning, info)

These types enable the admin UI to display processing issues from the database
and provide statistics for the issues dashboard.

templates/types.go

@@ -181,3 +181,23 @@ type Bookmark struct {
 	Notes         string
 	CreatedAt     time.Time
 }
+
+// ProcessingIssueData - Processing issue types
+type ProcessingIssueData struct {
+	ID               string
+	MediaItemID      string
+	Title            string
+	FilePath         string
+	FormatGroup      string
+	LibraryTypeName  string
+	IssueType        string
+	IssueDescription string
+	Severity         string
+	CreatedAt        time.Time
+}
+
+type IssueStats struct {
+	ErrorCount   int64
+	WarningCount int64
+	InfoCount    int64
+}