feat: Adds Latin1 text support (#2317)

## Summary

- Adds proper Latin1 encoding support, replacing CP1252 usage throughout the codebase
- Adds specialized, optimized string decoding methods with safe string filtering for each encoding type
- Filters invalid Unicode characters (C0/C1 control codes, non-characters) by removal rather than replacement since
the UO client renders nothing for these characters
- Fixes UTF-16 null terminator position handling to correctly advance by 2 bytes

## Changes

TextEncoding.cs

- Added SearchValues-based invalid byte/char detection for efficient filtering
- Added encoding-specific GetString methods: GetStringAscii, GetStringLatin1, GetStringUtf8, GetStringBigUni,
GetStringLittleUni
- Each method supports a safeString parameter for filtering invalid characters
- Little-endian UTF-16 uses direct memory cast for zero-copy decoding on LE systems
- Invalid characters are removed (not replaced with U+FFFD) since the client renders nothing for them

SpanReader.cs

- Added ReadLatin1() and ReadLatin1Safe() methods
- Rewrote encoding-specific read methods to use optimized TextEncoding.GetString* methods
- Fixed UTF-16 null terminator handling: position now correctly advances by byteLength (2) instead of 1

SpanWriter.cs

- Added WriteLatin1 and WriteLatin1Null methods

## Packet Updates

- Updated all packet code to use Latin1 encoding instead of CP1252
- Affected: account packets, equipment packets, menu packets, message packets, mobile packets, player packets, secure
trade packets, vendor packets, gump packets, book packets, mahjong packets

## Filtering Behavior

Invalid characters filtered in safe mode:
```
┌───────────────┬────────────────────────┐
│     Range     │      Description       │
├───────────────┼────────────────────────┤
│ 0x00-0x1F     │ C0 control codes       │
├───────────────┼────────────────────────┤
│ 0x7F          │ DEL                    │
├───────────────┼────────────────────────┤
│ 0x80-0x9F     │ C1 control codes       │
├───────────────┼────────────────────────┤
│ 0xFFFE-0xFFFF │ Unicode non-characters │
└───────────────┴────────────────────────┘
```

Note: Surrogate pairs (0xD800-0xDFFF) are not filtered because proper validation requires context checking for paired
vs unpaired surrogates. The UO client renders nothing for these anyway.

## Test Plan

- All 631 Server.Tests pass
- Verified client rendering behavior using TestUnicodeGump command (pages 1-5)
- Confirmed U+FFFD, unpaired surrogates, and non-characters all render as blank in client
- Verified Latin1 characters (0xA0-0xFF) display correctly
- Verified C1 control codes (0x80-0x9F) are filtered and don't display

Projects/Server/Network/Packets/OutgoingAccountPackets.cs

@@ -89,7 +89,7 @@ public static class OutgoingAccountPackets
                 var name = (m.RawName?.Trim()).DefaultIfNullOrEmpty("-no name-");
 
                 count++;
-                writer.WriteAscii(name, 30);
+                writer.WriteLatin1(name, 30);
                 writer.Clear(30); // Password (empty)
             }
         }
@@ -276,7 +276,7 @@ public static class OutgoingAccountPackets
             else
             {
                 var name = (m.RawName?.Trim()).DefaultIfNullOrEmpty("-no name-");
-                writer.WriteAscii(name, 30);
+                writer.WriteLatin1(name, 30);
                 writer.Clear(30); // password
             }
         }
@@ -341,7 +341,7 @@ public static class OutgoingAccountPackets
             else
             {
                 var name = (m.RawName?.Trim()).DefaultIfNullOrEmpty("-no name-");
-                writer.WriteAscii(name, 30);
+                writer.WriteLatin1(name, 30);
                 writer.Clear(30); // password
             }
         }
@@ -353,8 +353,8 @@ public static class OutgoingAccountPackets
             var ci = cityInfo[i];
 
             writer.Write((byte)i);
-            writer.WriteAscii(ci.City, textLength);
-            writer.WriteAscii(ci.Building, textLength);
+            writer.WriteLatin1(ci.City, textLength);
+            writer.WriteLatin1(ci.Building, textLength);
             if (client70130)
             {
                 writer.Write(ci.X);
@@ -428,7 +428,7 @@ public static class OutgoingAccountPackets
             var si = info[i];
 
             writer.Write((ushort)i);
-            writer.WriteAscii(si.Name, 32);
+            writer.WriteLatin1(si.Name, 32);
             writer.Write((byte)si.FullPercent);
             writer.Write((sbyte)si.TimeZone);
             // UO only supports IPv4