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/models/investment.rb

@@ -7,6 +7,8 @@ class Investment < ApplicationRecord
     "retirement" => { short: "Retirement", long: "Retirement" },
     "401k" => { short: "401(k)", long: "401(k)" },
     "roth_401k" => { short: "Roth 401(k)", long: "Roth 401(k)" },
+    "403b" => { short: "403(b)", long: "403(b)" },
+    "tsp" => { short: "TSP", long: "Thrift Savings Plan" },
     "529_plan" => { short: "529 Plan", long: "529 Plan" },
     "hsa" => { short: "HSA", long: "Health Savings Account" },
     "mutual_fund" => { short: "Mutual Fund", long: "Mutual Fund" },