fix(discord): resolve slash commands from interaction payload instead of gateway cache

Context.Guild in NetCord resolves the Guild object from the gateway client cache
(cache.Guilds.GetValueOrDefault(guildId)), not from the interaction JSON payload.
After a bot restart, the guild may not yet be cached when the first slash command
arrives, causing Context.Guild to be null even though the command is invoked
inside a guild channel. This produced "This command can only be used in a guild."

Changes:
- DiscordListSessionsCommand: use Context.Interaction.GuildId instead of Context.Guild.Id
- DiscordNewSessionCommand: use Context.Interaction.GuildId + REST GetGuildAsync/GetGuildUserAsync
- DiscordRescheduleCommand: same as above
- Bump version to 3.0.5

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

compose.yaml

@@ -49,7 +49,7 @@ services:
         crond -f
 
   bot:
-    image: git.codeanddice.ru/toutsu/gmrelay-bot:3.0.4
+    image: git.codeanddice.ru/toutsu/gmrelay-bot:3.0.5
     restart: always
     depends_on:
       db:
@@ -67,7 +67,7 @@ services:
       retries: 3
 
   discord:
-    image: git.codeanddice.ru/toutsu/gmrelay-discord-bot:3.0.4
+    image: git.codeanddice.ru/toutsu/gmrelay-discord-bot:3.0.5
     restart: always
     depends_on:
       db:
@@ -84,7 +84,7 @@ services:
       retries: 3
 
   web:
-    image: git.codeanddice.ru/toutsu/gmrelay-web:3.0.4
+    image: git.codeanddice.ru/toutsu/gmrelay-web:3.0.5
     restart: always
     depends_on:
       db: