fix(posts): normalize PostDate to yyyy-MM-dd HH:mm:ss GMT

Text-file exports can carry RFC 1123 dates ("Fri, 14 Feb 2025 15:20:09 GMT"),
which sort on the weekday name and fall outside --fromDate/--toDate
comparisons. PostDates.Normalize converts them on every PostDate write path
(AddPost, UpsertPostFromTextFile, UpdatePostContentFields).
normalize-postdate.sql fixes the 4 existing rows.

Co-Authored-By: Claude Opus 5 <[email protected]>

URLNotesGrabberCORE/DataAccess.cs

@@ -597,6 +597,7 @@ namespace URLNotesGrabberCORE
         {
             DBPath ??= GetDefaultDbPath();
             postType = PostTypes.Normalize(postType);
+            postDate = PostDates.Normalize(postDate)!;
             try { AddBlog(blogName, byLikes, DBPath); } catch { }
             try { UpdatePostSetDate(blogName, postID, postDate, DBPath); } catch { }
             try { UpdatePost(blogName, postID, reblogURL, postDate, postURL, slug, reblogKey, reblogName, summary, quote, body, tags, link, photoURL, photoCaption, downloadedFiles, audioCaption, question, answer, title, hasImage, byLikes, DBPath, rootBlogName, rootURL, postType); } catch { }
@@ -2249,6 +2250,7 @@ namespace URLNotesGrabberCORE
             // column. PostType is used as an output filename, so this is the invariant that keeps
             // a stray value from becoming a stray file.
             postType = PostTypes.Normalize(postType);
+            postDate = PostDates.Normalize(postDate);
             try { AddBlog(blogName, false, DBPath); } catch { }
 
             SQLiteConnection connection;
@@ -2620,10 +2622,11 @@ namespace URLNotesGrabberCORE
                 if (string.IsNullOrWhiteSpace(kvp.Value)) continue;
                 string? column = MapPrefixToColumn(kvp.Key);
                 if (column == null) continue;
+                string value = column == "PostDate" ? PostDates.Normalize(kvp.Value)! : kvp.Value;
                 string paramName = "@p" + parameters.Count;
                 setClauses.Add($"{column} = {paramName}");
                 changedClauses.Add($"IFNULL({column}, '') <> {paramName}");
-                parameters.Add((paramName, kvp.Value));
+                parameters.Add((paramName, value));
             }
 
             if (setClauses.Count == 0) return false;