Add audit log for moderation and admin actions

New audit_log table records actor, action, target and a JSON snapshot
of the details, so entries stay readable after the target is deleted;
the actor is set to NULL when the user is removed. logAudit() is called
from upload delete (single and bulk), comment delete, tag removal, role
create/delete, role permission changes, role assign/revoke and MOTD
updates. Logging failures only warn and never fail the action itself.

The admin page gets an audit card behind the new audit.view permission
with action filter, click-to-filter by user, readable summaries per
action and server-side pagination. Action catalog lives in
shared/utils/audit.ts, labels under admin.auditActions (de/en).

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/api/admin/roles/[id].delete.ts

@@ -3,7 +3,7 @@ import { roles } from '../../../db/schema'
 import { SYSTEM_ROLES } from '../../../../shared/utils/permissions'
 
 export default defineEventHandler(async (event) => {
-  await requirePermission(event, 'roles.manage')
+  const actor = await requirePermission(event, 'roles.manage')
   const id = Number(getRouterParam(event, 'id'))
   if (!Number.isInteger(id) || id <= 0) {
     throw createError({ statusCode: 400, statusMessage: 'Ungültige ID' })
@@ -17,5 +17,6 @@ export default defineEventHandler(async (event) => {
     throw createError({ statusCode: 400, statusMessage: `Die ${existing[0].name}-Rolle kann nicht gelöscht werden` })
   }
   await db.delete(roles).where(eq(roles.id, id))
+  await logAudit(actor.id, 'delete_role', { type: 'role', id }, { name: existing[0].name })
   return { ok: true }
 })