feat(dashboard): add traffic flow sankey chart (#5465)

* feat(dashboard): add traffic flow sankey chart

Add dashboard flow APIs and a Sankey-based flow view with user, optional API key, model, and channel layers.\n\nReuse the dashboard VChart palette, add precise link/node tooltips and interactions, and cover filtering, layer ordering, color stability, and error states with tests.

* feat: build flow chart from quota data

---------

Co-authored-by: CaIon <i@caion.me>

web/default/src/i18n/static-keys.ts

@@ -435,6 +435,10 @@ export const STATIC_I18N_KEYS = [
   'Data management and log viewing',
   'Dashboard',
   'System data statistics',
+  'Flow',
+  'Flow Filters',
+  'Filter the traffic flow view by time range and user.',
+  'Requests',
   'Token Management',
   'API token management',
   'Usage Logs',
@@ -490,6 +494,20 @@ export const STATIC_I18N_KEYS = [
   'Batch detection failed',
   'Batch detection complete: {{channels}} channels, {{add}} to add, {{remove}} to remove, {{fails}} failed',
 
+  // Dashboard flow stages (labels/descriptions passed to t at runtime)
+  'User',
+  'Node',
+  'Token',
+  'Group',
+  'Model',
+  'Channel',
+  'The user who made the requests',
+  'The deployment node that handled the requests',
+  'The API key used for the requests',
+  'The user group applied to the requests',
+  'The model that was requested',
+  'The upstream channel that served the requests',
+
   // Misc
   'Cancel',
   'Status',