Add global sync summary component for all providers (#588)

* Add shared sync statistics collection and provider sync summary UI

- Introduced `SyncStats::Collector` concern to centralize sync statistics logic, including account, transaction, holdings, and health stats collection.
- Added collapsible `ProviderSyncSummary` component for displaying sync summaries across providers.
- Updated syncers (e.g., `LunchflowItem::Syncer`) to use the shared collector methods for consistent stats calculation.
- Added rake tasks under `dev:sync_stats` for testing and development purposes, including fake stats generation with optional issues.
- Enhanced provider-specific views to include sync summaries using the new shared component.

* Refactor `ProviderSyncSummary` to improve maintainability

- Extracted `severity_color_class` to simplify severity-to-CSS mapping.
- Replaced `holdings_label` with `holdings_label_key` for streamlined localization.
- Updated locale file to separate `found` and `processed` translations for clarity.

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Josh Waldrep <joshua.waldrep5+github@gmail.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

app/views/lunchflow_items/_lunchflow_item.html.erb

@@ -82,6 +82,18 @@
           <%= render "accounts/index/account_groups", accounts: lunchflow_item.accounts %>
         <% end %>
 
+        <%# Sync summary (collapsible) - using shared ProviderSyncSummary component %>
+        <% stats = if defined?(@lunchflow_sync_stats_map) && @lunchflow_sync_stats_map
+             @lunchflow_sync_stats_map[lunchflow_item.id] || {}
+           else
+             lunchflow_item.syncs.ordered.first&.sync_stats || {}
+           end %>
+        <%= render ProviderSyncSummary.new(
+          stats: stats,
+          provider_item: lunchflow_item,
+          institutions_count: lunchflow_item.connected_institutions.size
+        ) %>
+
         <%# Use model methods for consistent counts %>
         <% unlinked_count = lunchflow_item.unlinked_accounts_count %>
         <% linked_count = lunchflow_item.linked_accounts_count %>