feat(editor): F4.5c the DHCP server and the port forwarding in the device sheet

Measured first: SheetRun now types into FILIUS' DHCP dialog and keeps rows
in its port forwarding dialog. Java's DHCP server keeps its bounds as typed
(".0.0.1" too), never takes an empty gateway or DNS server, hands out the
device's gateway and DNS server unless its own (a home router always its
LAN address, where "manual settings" do nothing), drops a second static
assignment of a MAC address silently and lets "_" through its MAC pattern;
the port forwarding dialog keeps any row, its firmware forwards only the
valid ones. Here a value passes its rule or is not taken, with a word why.

- doc: DHCP server addresses and flags, static assignments (a MAC address
  once, ignoring case), port forwarding rows (TCP or UDP, musterPort, the
  LAN address); the sheet shows what the server hands out and which rows
  Java's firmware forwards (the core's parsePortForwardingRow, exported)
- editor: Java's dialogs as pages of the sheet with a back button, the
  three row tables on one RowsEditor (the forwarding table rebuilt on it);
  a sheet per device, so an open page closes when another device is chosen

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

packages/doc/src/fields.ts

@@ -20,7 +20,7 @@
 
 import { IP_ADDRESS_PATTERN, javaIpCheck } from '@mdg-filius/core';
 
-export type FieldRule = 'name' | 'ipAddress' | 'ipAddressOrEmpty' | 'subnetMask' | 'ssid' | 'seconds' | 'port';
+export type FieldRule = 'name' | 'ipAddress' | 'ipAddressOrEmpty' | 'subnetMask' | 'ssid' | 'seconds' | 'port' | 'macAddress';
 
 /** What a field's text comes to: the value the device takes, or that it takes none. */
 export type CheckedField = { readonly value: string } | { readonly invalid: true };
@@ -31,6 +31,12 @@ const SUBNET_MASK_PATTERN = /^(0*([1-9]|1?[0-9]{1,2}|2[0-4]?[0-9]|25[0-5]))\.((0
 const SSID_PATTERN = /^[ -~]+$/;
 /** EingabenUeberpruefung.musterPort: 1 to 65535, no leading zero. */
 const PORT_PATTERN = /^([1-9]|[1-9][0-9]{1,3}|[1-5][0-9]{1,4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$/;
+/**
+ * EingabenUeberpruefung.musterMacAddress, whose class [0-9a-fA-f] also lets
+ * the six characters between Z and a through ("AA:BB:CC:DD:EE:_F"); here
+ * hexadecimal digits only.
+ */
+const MAC_ADDRESS_PATTERN = /^[0-9A-Fa-f]{2}(:[0-9A-Fa-f]{2}){5}$/;
 /** EingabenUeberpruefung.musterNurZahlen, at least one digit (Java's Long.parseLong refuses none). */
 const DIGITS_PATTERN = /^[0-9]+$/;
 
@@ -65,5 +71,8 @@ export function checkField(rule: FieldRule, text: string): CheckedField {
     }
     case 'port':
       return PORT_PATTERN.test(text.trim()) ? { value: text.trim() } : INVALID;
+    case 'macAddress':
+      // Upper case, as the model keeps MAC addresses (Java keeps them as typed and compares ignoring case).
+      return MAC_ADDRESS_PATTERN.test(text.trim()) ? { value: text.trim().toUpperCase() } : INVALID;
   }
 }