fix(fmt): decode the SIP002 plain-text password only once (#10520)

For a SIP002 link whose user info is "method:password" rather than
base64 (the 2022-blake3 form), ResolveSip002 unescapes the whole user
info and then unescapes the password a second time. A password that
still holds a valid percent sequence after the first pass decays:
p%41ss is written as p%2541ss and imported as pAss.

Same double-decoding as #10027 fixed for query values.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

v2rayN/ServiceLib/Handler/Fmt/ShadowsocksFmt.cs

@@ -165,7 +165,7 @@ public class ShadowsocksFmt : BaseFmt
                 return null;
             }
             item.SetProtocolExtra(item.GetProtocolExtra() with { SsMethod = userInfoParts.First() });
-            item.Password = Utils.UrlDecode(userInfoParts.Last());
+            item.Password = userInfoParts.Last();
         }
         else
         {