feat: Complete AEG-X-003 and verify AEG-X-004 readiness

AEG-X-003: Architecture Tests (COMPLETED)
✅ Added 6th rule: No duplicate aggregate IDs across modules
✅ All 6 architecture tests PASS:
  1. No prohibited source patterns (IGenericRepository, DateTime.Now, etc.)
  2. Domain isolation from infrastructure (no Dapper, Npgsql, FastEndpoints)
  3. SQL validation (no SELECT *, schema-qualified tables)
  4. Endpoint authorization (Roles or Policies required)
  5. No placeholder files (testfile, *.tmp)
  6. No duplicate aggregate IDs (new)

Acceptance_Evidence: Domain 기술의존 0, 모듈 직접 DB 접근 0, ID 중복 0 ✅

AEG-X-004: DbUp Recovery Rehearsal (Ready for DB Testing)
- Tests located: tests/KArtSell.Integration.Tests/DbUpMigrationTests.cs (570L)
- Covers 4 scenarios: Fresh install, Upgrade, Re-run, Failure recovery
- Infrastructure: Requires PostgreSQL + SSH tunnel for execution
- Evidence collection: Requires active DB connection (pending)

Phase 1 Progress:
- AEG-X-001: ✅ COMPLETED (VERSION_COVERAGE_MATRIX.md)
- AEG-X-002: ✅ COMPLETED (CI.yml formalized)
- AEG-X-003: ✅ COMPLETED (6 architecture tests PASS)
- AEG-X-004: 📋 READY FOR DB TESTING (test structure exists)
- AEG-X-005: 📋 PLANNED (next in sequence)

Cumulative Status: 3/5 = 60% Phase 1 complete (3h/15h estimated)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

tests/KArtSell.ArchitectureTests/RepositoryRulesTests.cs

@@ -107,6 +107,49 @@ public sealed class RepositoryRulesTests
             "Placeholder files are prohibited: " + string.Join(", ", names));
     }
 
+    [Fact]
+    public void Aggregate_ids_are_unique_across_modules()
+    {
+        var root = FindRepositoryRoot();
+        var aggregateIdFiles = Directory.EnumerateFiles(
+            Path.Combine(root, "src"),
+            "*.cs",
+            SearchOption.AllDirectories)
+            .Where(path => !IsGeneratedOrTestOutput(path))
+            .ToArray();
+
+        var aggregateIds = new Dictionary<string, List<string>>();
+
+        foreach (var file in aggregateIdFiles)
+        {
+            var text = File.ReadAllText(file);
+
+            // Match aggregate ID definitions: Guid("00000000-0000-0000-0000-...")
+            var pattern = @"Guid\(\""[a-f0-9\-]{36}\""";
+            var matches = System.Text.RegularExpressions.Regex.Matches(text, pattern);
+
+            foreach (System.Text.RegularExpressions.Match match in matches)
+            {
+                var id = match.Value;
+                if (!aggregateIds.TryGetValue(id, out var list))
+                {
+                    list = new List<string>();
+                    aggregateIds[id] = list;
+                }
+                list.Add(file);
+            }
+        }
+
+        var duplicates = aggregateIds
+            .Where(kvp => kvp.Value.Count > 1)
+            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+
+        Assert.True(duplicates.Count == 0,
+            duplicates.Count > 0
+                ? $"Duplicate aggregate IDs detected: {string.Join("; ", duplicates.Select(d => $"{d.Key} in {string.Join(", ", d.Value)}"))}"
+                : "No duplicate aggregate IDs found.");
+    }
+
     private static void AssertNoPattern(IEnumerable<string> files, string pattern, string message)
     {
         var violations = files