Korjaa ticket_fetch ja sähköpostien duplikaattiongelma

- Korjaa implode()-bugi: $email['to'] on string, ei array
- Lisää fetched_message_ids-taulu joka estää poistettujen
  tikettien uudelleenluonnin seuraavassa haussa
- Viestit haetaan postilaatikosta vain kertaalleen

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

db.php

@@ -358,6 +358,16 @@ function initDatabase(): void {
             INDEX idx_company (company_id)
         ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4",
 
+        "CREATE TABLE IF NOT EXISTS fetched_message_ids (
+            id INT AUTO_INCREMENT PRIMARY KEY,
+            company_id VARCHAR(50) NOT NULL,
+            message_id VARCHAR(512) NOT NULL,
+            fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE KEY uk_company_msgid (company_id, message_id),
+            FOREIGN KEY (company_id) REFERENCES companies(id) ON DELETE CASCADE,
+            INDEX idx_company (company_id)
+        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4",
+
         "CREATE TABLE IF NOT EXISTS customer_priority_emails (
             id INT AUTO_INCREMENT PRIMARY KEY,
             company_id VARCHAR(50) NOT NULL,
@@ -1640,6 +1650,22 @@ function dbDeleteTicketType(string $companyId, string $value): void {
     _dbExecute("DELETE FROM ticket_types WHERE company_id = ? AND value = ?", [$companyId, $value]);
 }
 
+// ==================== HAETUT MESSAGE-ID:T (duplikaattien esto) ====================
+
+function dbGetFetchedMessageIds(string $companyId): array {
+    $rows = _dbFetchAll("SELECT message_id FROM fetched_message_ids WHERE company_id = ?", [$companyId]);
+    $ids = [];
+    foreach ($rows as $r) { $ids[$r['message_id']] = true; }
+    return $ids;
+}
+
+function dbMarkMessageIdFetched(string $companyId, string $messageId): void {
+    if (empty($messageId)) return;
+    try {
+        _dbExecute("INSERT IGNORE INTO fetched_message_ids (company_id, message_id) VALUES (?, ?)", [$companyId, $messageId]);
+    } catch (\Throwable $e) { /* duplicate, ok */ }
+}
+
 // ==================== YRITYKSEN API-ASETUKSET ====================
 
 function dbGetCompanyConfig(string $companyId): array {