feat: add CSV import for student event rankings

Let advisors load preference ranks from a converted CSV with fuzzy matching, known aliases, and a parse-preview-save page instead of relying on the ranking editor.

Co-authored-by: Cursor <cursoragent@cursor.com>

Core/Models/StudentEventRankingParseResult.cs

@@ -0,0 +1,107 @@
+using Core.Entities;
+
+namespace Core.Models;
+
+/// <summary>
+/// Result of parsing a student event ranking CSV.
+/// </summary>
+public class StudentEventRankingParseResult
+{
+    /// <summary>
+    /// Accepted ranking matches, including the raw CSV text and fuzzy scores.
+    /// </summary>
+    public List<StudentEventRankingMatch> Matches { get; set; } = [];
+
+    /// <summary>
+    /// Unmatched students, unmatched or ambiguous events, and other row-level issues.
+    /// </summary>
+    public List<StudentEventRankingIssue> Issues { get; set; } = [];
+
+    /// <summary>
+    /// Critical errors that prevented parsing (for example a missing header).
+    /// </summary>
+    public List<string> Errors { get; set; } = [];
+
+    /// <summary>
+    /// Non-critical warnings about the file as a whole.
+    /// </summary>
+    public List<string> Warnings { get; set; } = [];
+
+    /// <summary>
+    /// Accepted rankings without match metadata.
+    /// </summary>
+    public IReadOnlyList<StudentEventRanking> Rankings => [.. Matches.Select(m => m.Ranking)];
+
+    /// <summary>
+    /// Number of accepted ranking rows.
+    /// </summary>
+    public int TotalParsed => Matches.Count;
+
+    /// <summary>
+    /// Distinct students who have at least one accepted rank.
+    /// Uses Id when assigned, otherwise first and last name, so unsaved parsed students stay distinct.
+    /// </summary>
+    public IReadOnlyList<Student> StudentsWithAcceptedRanks =>
+        [.. Matches
+            .Select(m => m.Ranking.Student)
+            .GroupBy(s => s.Id != 0 ? $"id:{s.Id}" : $"name:{s.FirstName}|{s.LastName}")
+            .Select(g => g.First())];
+
+    /// <summary>
+    /// True when no critical parse errors were recorded.
+    /// </summary>
+    public bool IsSuccess => Errors.Count == 0;
+}
+
+/// <summary>
+/// A successfully matched ranking cell from the CSV.
+/// </summary>
+public class StudentEventRankingMatch
+{
+    public required StudentEventRanking Ranking { get; set; }
+
+    public string RawStudentName { get; set; } = string.Empty;
+
+    public string RawEventName { get; set; } = string.Empty;
+
+    public int StudentScore { get; set; }
+
+    public int EventScore { get; set; }
+
+    public int RowNumber { get; set; }
+}
+
+/// <summary>
+/// A row-level problem encountered while parsing rankings.
+/// </summary>
+public class StudentEventRankingIssue
+{
+    public int RowNumber { get; set; }
+
+    public int Rank { get; set; }
+
+    public string RawStudentName { get; set; } = string.Empty;
+
+    public string RawEventName { get; set; } = string.Empty;
+
+    public StudentEventRankingIssueType IssueType { get; set; }
+
+    public string Message { get; set; } = string.Empty;
+
+    public string? SuggestedEventName { get; set; }
+
+    public int? Score { get; set; }
+}
+
+/// <summary>
+/// Types of issues reported while parsing student event rankings.
+/// </summary>
+public enum StudentEventRankingIssueType
+{
+    UnmatchedStudent,
+    UnmatchedEvent,
+    AmbiguousEvent,
+    DuplicateEvent,
+    DuplicateRank,
+    InvalidFormat
+}