Add IPMI FRU editor to Tools page

- New card "IPMI — FRU" on Tools page (device 0, in-band)
- Read: GET /api/tools/ipmi-fru → ipmitool fru print 0 → editable table
- Editable fields: chassis (part#, serial, extra), board (mfr, product, serial, part#),
  product (mfr, name, part#, version, serial); read-only fields displayed as text
- Write: POST /api/tools/ipmi-fru/write → task → backup to fru-backups/ → ipmitool fru edit per field
- Dirty tracking + Save (N changed) button, same UX as Supermicro DMI card

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/server.go

@@ -316,6 +316,8 @@ func NewHandler(opts HandlerOptions) http.Handler {
 	mux.HandleFunc("POST /api/tools/nvme-format/run", h.handleAPINVMeFormatRun)
 	mux.HandleFunc("GET /api/tools/saa-dmi", h.handleAPISAADMIRead)
 	mux.HandleFunc("POST /api/tools/saa-dmi/write", h.handleAPISAADMIWrite)
+	mux.HandleFunc("GET /api/tools/ipmi-fru", h.handleAPIIPMIFRURead)
+	mux.HandleFunc("POST /api/tools/ipmi-fru/write", h.handleAPIIPMIFRUWrite)
 
 	// GPU presence / tools
 	mux.HandleFunc("GET /api/gpu/presence", h.handleAPIGPUPresence)