fix: SkillsUsage 页面样式修复与 API server skill usage 统计 (#698)

* Reapply "feat: 新增 Skills Usage 监控统计与图表 (#668)" (#670)

This reverts commit 91de3b12a1.

* fix: count API-server skill usage

* fix: align SkillsUsageView header with other pages and update sidebar icon

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Zhicheng Han <zhicheng.han@mathematik.uni-goettingen.de>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/server/src/controllers/hermes/skills.ts

@@ -6,6 +6,7 @@ import {
   safeReadFile, extractDescription, listFilesRecursive, getHermesDir,
 } from '../../services/config-helpers'
 import { pinSkill } from '../../services/hermes/hermes-cli'
+import { getSkillUsageStatsFromDb } from '../../db/hermes/sessions-db'
 
 /** Read bundled manifest as a name→hash map from ~/.hermes/skills/.bundled_manifest */
 function readBundledManifest(manifestContent: string | null): Map<string, string> {
@@ -239,6 +240,18 @@ export async function list(ctx: any) {
   }
 }
 
+export async function usageStats(ctx: any) {
+  const rawDays = parseInt(String(ctx.query?.days ?? '7'), 10)
+  const days = Number.isFinite(rawDays) && rawDays > 0 ? Math.min(rawDays, 365) : 7
+
+  try {
+    ctx.body = await getSkillUsageStatsFromDb(days)
+  } catch (err: any) {
+    ctx.status = 500
+    ctx.body = { error: `Failed to read skill usage stats: ${err.message}` }
+  }
+}
+
 export async function toggle(ctx: any) {
   const { name, enabled } = ctx.request.body as { name?: string; enabled?: boolean }
   if (!name || typeof enabled !== 'boolean') {