Demo data realism + invoice resend via SMS on any status

Seed data fixes:
- Fix EF interceptor: no longer overwrites explicitly-set CreatedAt on Added
  entities — root cause of all "same month" chart issues
- Customer seeder: generates 15 customers/month from Jan → current month;
  keeps 10 commercial anchors in deterministic order for job seeder index map
- Invoice seeder: historical range bumped from 2→8 paid invoices/month so
  P&L shows consistent profit (~$5,200 collected vs ~$4,200 monthly expenses)
- Month -1 bumped to 7 paid invoices to stay above expenses
- Jobs: set UpdatedAt to historical event date so analytics don't need null fallback
- Analytics (ReportsController): use CompletedDate ?? UpdatedAt ?? CreatedAt for
  revenue chart grouping; fixes empty Revenue Trend charts on Overview/Revenue tabs
- SeedDataService: inject IAccountBalanceService; auto-recalculate account balances
  after seeding; patch checking/savings opening balances unconditionally on reset
- Customer list: sort by CompanyName ?? ContactLastName so individuals and
  commercial accounts interleave instead of appearing as two blocks

Invoice resend:
- ResendInvoice action now accepts sendEmail + sendSms parameters; SMS-only
  resend no longer requires an email address on file
- Ensures PublicViewToken exists before SMS so the view link is always valid
- canResend in Details view now allows Paid invoices (removed != Paid guard)
- Resend button shows channel-choice modal when customer has both email + SMS,
  direct SMS button when SMS only, or email button when email only
- New #resendChannelModal mirrors the Send channel modal but posts to ResendInvoice
- resendInvoice() JS updated to pass sendEmail/sendSms query params

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

src/PowderCoating.Web/Controllers/SeedDataController.cs

@@ -137,7 +137,7 @@ public class SeedDataController : Controller
                 OperatingCosts = true,
                 Bills          = true,
                 Expenses       = true,
-                Workers        = true,
+                Workers        = false,  // workers stay static — never deleted on reset
                 Vendors        = true,
                 NamedOvens     = true,
                 Appointments   = true,