feat: revamp analytics dashboards and harden database migrations

Add dashboard and overview analytics, health monitoring, provider expense tracking, and announcement updates across the gateway and frontend.

Keep schema migrations free of historical backfills while preserving automatic backfill execution. Bound migration deadlines, run schema preparation before Compose replacement, and anonymize deleted dashboard users.

Include the current documentation cleanup and regression coverage.

frontend/src/api/usage.ts

@@ -133,6 +133,8 @@ export interface UsageByApiFormat {
 }
 
 export interface UsageFilters {
+  from?: string
+  to?: string
   user_id?: string // UUID
   provider_id?: string // UUID
   model?: string
@@ -499,6 +501,17 @@ export const usageApi = {
   },
 
   async getAllUsageRecords(params?: {
+    from?: string
+    to?: string
+    provider_id?: string
+    api_key_id?: string
+    request_id?: string
+    attribution_kind?: string
+    endpoint_kind?: string
+    request_type?: string
+    is_stream?: boolean
+    has_format_conversion?: boolean
+    slow_threshold_ms?: number
     start_date?: string
     end_date?: string
     preset?: string
@@ -539,6 +552,17 @@ export const usageApi = {
   },
 
   async getAllUsageRecordTotal(params?: {
+    from?: string
+    to?: string
+    provider_id?: string
+    api_key_id?: string
+    request_id?: string
+    attribution_kind?: string
+    endpoint_kind?: string
+    request_type?: string
+    is_stream?: boolean
+    has_format_conversion?: boolean
+    slow_threshold_ms?: number
     start_date?: string
     end_date?: string
     preset?: string
@@ -576,7 +600,7 @@ export const usageApi = {
    */
   async getActiveRequests(
     ids?: string[],
-    timeRange?: Pick<UsageFilters, 'start_date' | 'end_date' | 'preset' | 'timezone' | 'tz_offset_minutes'>
+    timeRange?: Pick<UsageFilters, 'from' | 'to' | 'start_date' | 'end_date' | 'preset' | 'timezone' | 'tz_offset_minutes'>
   ): Promise<{
     requests: Array<{
       id: string
@@ -629,6 +653,10 @@ export const usageApi = {
     if (ids?.length) {
       params.ids = ids.join(',')
     }
+    if (timeRange?.from && timeRange.to) {
+      params.from = timeRange.from
+      params.to = timeRange.to
+    }
     if (timeRange?.start_date) {
       params.start_date = timeRange.start_date
     }