fix: remove manual project creation, smart sequence release, received-invoices schema fix

- Remove ProjectCreate page, POST /projects endpoint, and next-number endpoint
- Projects can only be created through orders (shared numbering sequence)
- Remove dead CreateProjectSchema and createProject service function
- Delete 'order' row from number_sequences (unused; code uses 'shared')
- Smart sequence release: decrement last_number only when deleting the highest number
- Fix received-invoices stats referencing non-existent is_deleted and amount_czk columns
- Update deploy instructions in CLAUDE.md (npm install, prisma migrate deploy)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/services/invoices.service.ts

@@ -493,7 +493,7 @@ export async function deleteInvoice(id: number) {
   const year = existing.invoice_number
     ? Number(existing.invoice_number.split("/")[1]) || new Date().getFullYear()
     : new Date().getFullYear();
-  await releaseInvoiceNumber(year);
+  await releaseInvoiceNumber(year, existing.invoice_number ?? undefined);
 
   return existing;
 }