fix: Nordea Business CSV variants, API keys UI polish, transaction categorization (#183)

* fix: MCP OAuth 303 redirect, send dialog auto-close, bank details null payload

- OAuth authorize: use 303 See Other instead of default 307, which
  preserved POST method and caused Claude's callback to return 405
- SendInvoiceDialog: close dialog and show toast after email send
  instead of leaving a success message that requires manual close
- BankDetailsSetupDialog: omit empty fields from payload instead of
  sending null, which fails Zod validation on non-nullable schema fields

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* refactor: remove dead sentMessage state and fix stale comment

Remove sentMessage state, its success banner JSX, and the CheckCircle2
import — all unreachable after the dialog now auto-closes on email send.
Fix stale "to null" comment in BankDetailsSetupDialog.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: support Nordea Business CSV variants, polish API keys UI, fix transaction categorization

- Extend Nordea Business bank file parser to handle three CSV export
  formats (classic, Betalare/Mottagare variant, Bokföringsdatum variant)
  with proper detection guards against SEB/LF misidentification
- Rework ApiKeysPanel: add CopyBlock component, destructive confirm on
  revoke, collapsible API-key-based connection methods, Claude.ai OAuth
  instructions as recommended path, simplified scope badges
- Stop deriving is_business from category on manual transaction creation;
  set null so categorization flow handles it correctly
- Show categorize button when journal_entry_id is missing regardless of
  is_business value

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: address PR review — await clipboard, fix zero-scope label, simplify condition

- Await navigator.clipboard.writeText and catch failures
- Change zero-scope label from "Enbart läs" to "Inga behörigheter"
- Simplify redundant ternary condition in TransactionHistoryList

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: repair broken ternary in TransactionHistoryList JSX

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/(dashboard)/transactions/page.tsx

@@ -488,7 +488,7 @@ export default function TransactionsPage() {
         amount: data.amount,
         currency: data.currency,
         category: data.category || 'uncategorized',
-        is_business: data.is_business,
+        is_business: null,
         notes: data.notes,
       })
       .select()