Feat: /import endpoint & drag-n-drop imports (#501)

* Implement API v1 Imports controller

- Add Api::V1::ImportsController with index, show, and create actions
- Add Jbuilder views for index and show
- Add integration tests
- Implement row generation logic in create action
- Update routes

* Validate import account belongs to family

- Add validation to Import model to ensure account belongs to the same family
- Add regression test case in Api::V1::ImportsControllerTest

* updating docs to be more detailed

* Rescue StandardError instead of bare rescue in ImportsController

* Optimize Imports API and fix documentation

- Implement rows_count counter cache for Imports
- Preload rows in Api::V1::ImportsController#show
- Update documentation to show correct OAuth scopes

* Fix formatting in ImportsControllerTest

* Permit all import parameters and fix unknown attribute error

* Restore API routes for auth, chats, and messages

* removing pr summary

* Fix trailing whitespace and configured? test failure

- Update Import#configured? to use rows_count for performance and consistency
- Mock rows_count in TransactionImportTest
- Fix trailing whitespace in migration

* Harden security and fix mass assignment in ImportsController

- Handle type and account_id explicitly in create action
- Rename import_params to import_config_params for clarity
- Validate type against Import::TYPES

* Fix MintImport rows_count update and migration whitespace

- Update MintImport#generate_rows_from_csv to update rows_count counter cache
- Fix trailing whitespace and final newline in AddRowsCountToImports migration

* Implement full-screen Drag and Drop CSV import on Transactions page

- Add DragAndDropImport Stimulus controller listening on document
- Add full-screen overlay with icon and text to Transactions index
- Update ImportsController to handle direct file uploads via create action
- Add system test for drag and drop functionality

* Implement Drag and Drop CSV upload on Import Upload page

- Add drag-and-drop-import controller to import/uploads/show
- Add full-screen overlay to import/uploads/show
- Annotate upload form and input with drag-and-drop targets
- Add PR_SUMMARY.md

* removing pr summary

* Add file validation to ImportsController

- Validate file size (max 10MB) and MIME type in create action
- Prevent memory exhaustion and invalid file processing
- Defined MAX_CSV_SIZE and ALLOWED_MIME_TYPES in Import model

* Refactor dragLeave logic with counter pattern to prevent flickering

* Extract shared drag-and-drop overlay partial

- Create app/views/imports/_drag_drop_overlay.html.erb
- Update transactions/index and import/uploads/show to use the partial
- Reduce code duplication in views

* Update Brakeman and harden ImportsController security

- Update brakeman to 7.1.2
- Explicitly handle type assignment in ImportsController#create to avoid mass assignment
- Remove :type from permitted import parameters

* Fix trailing whitespace in DragAndDropImportTest

* Don't commit LLM comments as file

* FIX add api validation

---------

Co-authored-by: Carlos Adames <cj@Carloss-MacBook-Air.local>
Co-authored-by: Juan José Mata <jjmata@jjmata.com>
Co-authored-by: sokie <sokysrm@gmail.com>

app/views/transactions/index.html.erb

@@ -46,10 +46,18 @@
   <%= render "summary", totals: @search.totals %>
 
   <div id="transactions"
-       data-controller="bulk-select checkbox-toggle"
+       data-controller="bulk-select checkbox-toggle drag-and-drop-import"
        data-bulk-select-singular-label-value="<%= t(".transaction") %>"
        data-bulk-select-plural-label-value="<%= t(".transactions") %>"
-       class="flex flex-col bg-container rounded-xl shadow-border-xs px-3 py-4 lg:p-4">
+       class="flex flex-col bg-container rounded-xl shadow-border-xs px-3 py-4 lg:p-4 relative group">
+
+    <%= form_with url: imports_path, method: :post, class: "hidden", data: { drag_and_drop_import_target: "form" } do |f| %>
+      <%= f.hidden_field "import[type]", value: "TransactionImport" %>
+      <%= f.file_field "import[csv_file]", class: "hidden", data: { drag_and_drop_import_target: "input" }, accept: ".csv" %>
+    <% end %>
+
+    <%= render "imports/drag_drop_overlay", title: "Drop CSV to import", subtitle: "Upload transactions directly" %>
+
     <%= render "transactions/searches/search" %>
 
     <div id="entry-selection-bar" data-bulk-select-target="selectionBar" class="flex justify-center hidden">