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/UOContent/Network/Packets/IncomingAccountPackets.cs

@@ -63,7 +63,7 @@ public static class IncomingAccountPackets
         var unk2 = reader.ReadInt32();
         int unk3 = reader.ReadByte();
         */
-        var name = reader.ReadAscii(30);
+        var name = reader.ReadLatin1Safe(30);
 
         reader.Seek(2, SeekOrigin.Current);
         var flags = reader.ReadInt32();
@@ -371,8 +371,8 @@ public static class IncomingAccountPackets
         state.Version = ap.Version;
         state.Seeded = true;
 
-        var username = reader.ReadAscii(30);
-        var password = reader.ReadAscii(30);
+        var username = reader.ReadLatin1Safe(30);
+        var password = reader.ReadLatin1Safe(30);
 
         var e = new GameServer.GameLoginEventArgs(state, username, password);
 
@@ -446,8 +446,8 @@ public static class IncomingAccountPackets
 
         state.SentFirstPacket = true;
 
-        var username = reader.ReadAscii(30);
-        var password = reader.ReadAscii(30);
+        var username = reader.ReadLatin1Safe(30);
+        var password = reader.ReadLatin1Safe(30);
 
         var accountLoginEventArgs = new AccountLoginEventArgs(state, username, password);
 

Projects/UOContent/Network/Packets/IncomingMessagePackets.cs

@@ -40,7 +40,7 @@ public static class IncomingMessagePackets
         var type = (MessageType)reader.ReadByte();
         int hue = reader.ReadInt16();
         reader.ReadInt16(); // font
-        var text = reader.ReadAsciiSafe().Trim();
+        var text = reader.ReadLatin1Safe().Trim();
 
         if (text.Length is <= 0 or > 128)
         {

Projects/UOContent/Network/Packets/IncomingMobilePackets.cs

@@ -36,7 +36,7 @@ public static class IncomingMobilePackets
 
         if (targ != null)
         {
-            RenameRequests.RenameRequest(from, targ, reader.ReadAsciiSafe());
+            RenameRequests.RenameRequest(from, targ, reader.ReadLatin1Safe());
         }
     }
 

Projects/UOContent/Network/Packets/IncomingPlayerPackets.cs

@@ -223,7 +223,7 @@ public static class IncomingPlayerPackets
         var serial = reader.ReadUInt32();
         var prompt = reader.ReadInt32();
         var type = reader.ReadInt32();
-        var text = reader.ReadAsciiSafe();
+        var text = reader.ReadLatin1Safe();
 
         if (text.Length > 128)
         {