UI Suggestions for Account Types in Setup Modal + Stats-Based Inactive Handling (#368)

* - Add tests for `Simplefin::AccountTypeMapper` and `AccountSimplefinCreation`
- Implement `Simplefin::AccountTypeMapper` for account type inference with fallback-only logic
- Enhance inactive state handling for `SimplefinItem::Importer`
- Improve subtype selection handling in views with confidence-based inference

* Remove unnecessary `.presence` check for `openai_uri_base` in hostings settings

* Refine zero balance detection logic in `SimplefinItem::Importer` and add regression test for missing balances scenario

* Enhance account type and subtype inference logic with explicit investment subtype mapping, improved regex handling, and institution-based credit card detection

* Refine retirement subtype mapping in `AccountTypeMapper` tests with explicit case-based assertions

* Expand `AccountTypeMapper` investment subtype mapping to include `403b` and `tsp` with updated regex definitions

* Remove unused `retirement_hint?` method in `AccountTypeMapper` to simplify codebase

---------

Co-authored-by: Josh Waldrep <joshua.waldrep5+github@gmail.com>

app/views/simplefin_items/setup_accounts.html.erb

@@ -78,8 +78,10 @@
               <div>
                 <%= label_tag "account_types[#{simplefin_account.id}]", "Account Type:",
                              class: "block text-sm font-medium text-primary mb-2" %>
+                <% inferred = @inferred_map[simplefin_account.id] || {} %>
+                <% selected_type = inferred[:confidence] == :high ? inferred[:type] : "" %>
                 <%= select_tag "account_types[#{simplefin_account.id}]",
-                              options_for_select(@account_type_options),
+                              options_for_select(@account_type_options, selected_type),
                               { class: "appearance-none bg-container border border-primary rounded-md px-3 py-2 text-sm leading-6 text-primary focus:border-primary focus:ring-1 focus:ring-primary focus:outline-none w-full",
                                 data: {
                                   action: "change->account-type-selector#updateSubtype"