Support attaching a file / pasting a screenshot when creating a new ticket

The "New ticket" modal only took a plain-text message. It now matches the
existing reply box on an open ticket: a "Прикрепить файл" button, and Ctrl+V
paste of a clipboard screenshot attaches it directly. POST /api/tickets
switched from JSON to multipart/form-data to carry the optional file,
reusing the same saveAttachment/attachment-delivery path replies already use.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GteWhnWKTmnXcsd5jx6H7u

src/lib/tickets/service.ts

@@ -619,6 +619,7 @@ export async function createManualTicket(params: {
   body: string;
   customerName: string;
   customerEmail?: string;
+  attachment?: AttachmentInput;
 }) {
   const [customer] = await db
     .insert(customers)
@@ -642,6 +643,7 @@ export async function createManualTicket(params: {
     authorName: params.customerName,
     body: params.body,
     direction: "in",
+    attachments: params.attachment ? [params.attachment] : undefined,
   });
 }