Add format-agnostic SourceText support to entities and DTOs

- Add SourceText and SourcePluralText fields to ResourceKey entity
- Update ResourceKeyDto and TranslationDto with SourceText properties
- Add SourceText/SourcePluralText to KeySyncDtos for sync operations

Author: nickprotop

cloud/src/LrmCloud.Api/Services/Translation/CloudTranslationService.cs

@@ -213,13 +213,27 @@ public async Task<TranslateResponseDto> TranslateKeysAsync(
                     }
                     else
                     {
-                        // Look up source translation - check both conventions:
-                        // - CLI sync stores default language with LanguageCode = ""
-                        // - Web import stores with actual code (e.g., "en")
-                        var sourceTranslation = key.Translations
-                            .FirstOrDefault(t => (t.LanguageCode == sourceLanguageDbCode || t.LanguageCode == sourceLanguage)
-                                                 && t.PluralForm == pluralForm);
-                        sourceText = sourceTranslation?.Value;
+                        // Priority 1: Use ResourceKey.SourceText (format-agnostic source)
+                        if (string.IsNullOrEmpty(pluralForm) && !string.IsNullOrEmpty(key.SourceText))
+                        {
+                            sourceText = key.SourceText;
+                        }
+                        // Priority 2: Use ResourceKey.SourcePluralText for plural "other" form
+                        else if (pluralForm == "other" && !string.IsNullOrEmpty(key.SourcePluralText))
+                        {
+                            sourceText = key.SourcePluralText;
+                        }
+                        // Priority 3: Fall back to translation lookup (backward compatibility)
+                        else
+                        {
+                            // Look up source translation - check both conventions:
+                            // - CLI sync stores default language with LanguageCode = ""
+                            // - Web import stores with actual code (e.g., "en")
+                            var sourceTranslation = key.Translations
+                                .FirstOrDefault(t => (t.LanguageCode == sourceLanguageDbCode || t.LanguageCode == sourceLanguage)
+                                                     && t.PluralForm == pluralForm);
+                            sourceText = sourceTranslation?.Value;
+                        }
                     }
 
                     // Skip empty source texts (but don't skip the whole key for plurals)

cloud/src/LrmCloud.Shared/DTOs/Resources/ResourceKeyDto.cs

@@ -10,6 +10,10 @@ public class ResourceKeyDto
     public string? KeyPath { get; set; }
     public bool IsPlural { get; set; }
     /// <summary>
+    /// Source text for this key (value from default language file, msgid for PO format).
+    /// </summary>
+    public string? SourceText { get; set; }
+    /// <summary>
     /// For plural keys, the source plural text pattern (PO msgid_plural or "other" form).
     /// </summary>
     public string? SourcePluralText { get; set; }

cloud/src/LrmCloud.Shared/DTOs/Resources/TranslationDto.cs

@@ -19,4 +19,10 @@ public class TranslationDto
     /// Translation-specific comment (per-language note).
     /// </summary>
     public string? Comment { get; set; }
+
+    /// <summary>
+    /// True if this translation was synthesized (e.g., from SourceText for display),
+    /// not stored in the database.
+    /// </summary>
+    public bool IsVirtual { get; set; }
 }

cloud/src/LrmCloud.Shared/DTOs/Sync/KeySyncDtos.cs

@@ -68,6 +68,12 @@ public class EntryChangeDto
     /// </summary>
     public Dictionary<string, string>? PluralForms { get; set; }
 
+    /// <summary>
+    /// Source text for the key (value from default language, msgid for PO format).
+    /// Only set when pushing from source/default language.
+    /// </summary>
+    public string? SourceText { get; set; }
+
     /// <summary>
     /// For plural keys, the source plural text pattern (PO msgid_plural or "other" form).
     /// Only set when pushing from source/default language.
@@ -285,6 +291,11 @@ public class EntryDataDto
     /// </summary>
     public bool IsPlural { get; set; }
 
+    /// <summary>
+    /// Source text for the key (value from default language, msgid for PO format).
+    /// </summary>
+    public string? SourceText { get; set; }
+
     /// <summary>
     /// For plural keys, the source plural text pattern (PO msgid_plural or "other" form).
     /// </summary>

cloud/src/LrmCloud.Shared/Entities/ResourceKey.cs

@@ -32,6 +32,13 @@ public class ResourceKey
     [Column("is_plural")]
     public bool IsPlural { get; set; }
 
+    /// <summary>
+    /// Source text for this key (value from default language file, msgid for PO format).
+    /// This is the authoritative source text used for translation.
+    /// </summary>
+    [Column("source_text")]
+    public string? SourceText { get; set; }
+
     /// <summary>
     /// For plural keys, stores the source plural text pattern.
     /// For PO format: this is the msgid_plural value.