fix(support): hide TransactionIssue + LimitRequest from ticket menu

[Blume1977]

Summary

Both TransactionIssue and LimitRequest options in the in-app support ticket type picker silently fail with HTTP 400 on submit because the app never sends the API-required nested DTOs (transaction / limitRequest). The reproduction in the field is RealUnitApiException: limitRequest should not be empty (statusCode: 400) for LimitRequest; the TransactionIssue equivalent has not surfaced because realunit-app users typically file transaction issues via services.dfx.swiss instead.

This PR hides both options from the picker until the proper forms are implemented. The enum values, i18n keys (supportTransactionIssue, supportLimitRequest), icons, and the cubit's _getTicketName mapping are intentionally left in place so re-enabling is a one-tuple revert per type once the structured input UI (dropdowns, transaction picker, document upload) lands.

Why not implement the forms now

• LimitRequest needs three dropdowns (limit / investmentDate / fundOrigin), an optional fundOriginText field mapped from message, a KYC ≥ 50 gate, and a mandatory document upload (PNG / JPEG / PDF). Requires a new file_picker dependency for PDF support.
• TransactionIssue needs a transaction picker (list of the user's recent transactions via GET /v1/transactions) plus a reason dropdown filtered to [FundsNotReceived, TransactionMissing, Other].
• Both are independent feature PRs of meaningful scope; hiding now removes the user-facing failure immediately.

Scope

• lib/screens/support/subpages/support_create_ticket_page.dart — remove two tuples from the items: array of TagSelection<SupportIssueType>.
• No API, model, cubit, service, or i18n changes.

Test plan

• flutter analyze → No issues found! (ran in 4.7s)
• flutter test test/screens/support/ → 62 / 62 passed
• Manual smoke: open Neues Ticket erstellen, confirm only Allgemeines Anliegen, Fehlerbericht, KYC-Problem are selectable.
• Manual smoke: submit each of the three remaining types with a short message and verify a ticket is created (no 400).