Fix hardcoded user-facing strings — localize email fallbacks, API errors, AI parse messages

- Frontend: update extractApiError to check body.code first via i18n 'error.<code>' keys;
  add en/ro translations for cv_file_missing, captcha_verification_failed, request_cancelled
- email-data migration: seed 6 fallback template keys (match N/A, subject label, unknown IP,
  job search results empty states for keywords/providers/location)
- EmailApiEmailSender: replace "N/A", "Job", "Unknown" literals with template lookups
- CvSearchEmailSender: replace "none detected", "none", "-" literals with template lookups
- cv-matcher-data migration: seed parse-error.summary and parse-error.recommendation in AiPrompts
- CvMatcherService: look up localized parse-error messages from AiPrompts before calling ParseResult

Closes #53

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Apis/cv-matcher-api/Services/CvMatcherService.cs

@@ -141,7 +141,9 @@ public sealed class CvMatcherService : ICvMatcherService
             """;
 
         var json = await _ai.CreateChatCompletionAsync(systemPrompt, userPrompt, 0.2m, ct);
-        var result = ParseResult(json);
+        var errorSummary = await _aiPrompts.GetAsync("parse-error.summary", language, ct);
+        var errorRec     = await _aiPrompts.GetAsync("parse-error.recommendation", language, ct);
+        var result = ParseResult(json, errorSummary, errorRec);
         result.JobDocumentId = job.Id;
         result.JobUrl = job.SourceUrl;
         result.Cached = false;
@@ -153,7 +155,10 @@ public sealed class CvMatcherService : ICvMatcherService
     /// Deserialises the LLM's JSON output into a <see cref="JobMatchResponse"/>.
     /// Returns a safe fallback response instead of throwing when the JSON cannot be parsed.
     /// </summary>
-    private static JobMatchResponse ParseResult(string json)
+    private static JobMatchResponse ParseResult(
+        string json,
+        string? errorSummary = null,
+        string? errorRec = null)
     {
         try
         {
@@ -168,8 +173,8 @@ public sealed class CvMatcherService : ICvMatcherService
         return new JobMatchResponse
         {
             Score = 0,
-            Summary = "The AI response could not be parsed as structured JSON.",
-            Recommendations = ["Inspect the raw model output and tune the scoring prompt."]
+            Summary = errorSummary ?? "The AI response could not be parsed as structured JSON.",
+            Recommendations = [errorRec ?? "Inspect the raw model output and tune the scoring prompt."]
         };
     }