Remove hardcoded secrets; source credentials from configuration

The Telegram bot token was a const in AddChannels(), and the Mistral API
key was baked into the embedded Provider.Mistral.toml resource.

- Wire AddChannels() through the existing (previously unused)
  AddTelegramOptions(), which binds "Channels:Telegram" and validates on
  start. TelegramOptions is resolved from IOptions<> so TelegramAdapter
  and TelegramChannel are unchanged.
- Ship the embedded provider defaults with an empty ApiKey. Ollama's
  placeholder is now a non-secret literal.
- Re-apply AddEnvironmentVariables() last in AddLunaConfiguration() so
  env vars override the TOML sources; without this the embedded defaults
  would shadow injected credentials.

Credentials are now supplied via Providers__Mistral__ApiKey and
Channels__Telegram__BotToken, or via ~/.luna/providers/*.toml overrides.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Luna.Channels/Extensions/ServiceCollectionExtensions.cs

@@ -1,25 +1,27 @@
 using Luna.Channels.Abstractions;
 using Luna.Channels.Telegram;
 using Luna.Configuration;
+using Luna.Configuration.Extensions;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
 using Telegram.Bot;
 
 namespace Luna.Channels.Extensions;
 
 public static class ServiceCollectionExtensions
 {
-    private const string TelegramBotToken = "REDACTED-TELEGRAM-BOT-TOKEN";
-
     extension(IServiceCollection services)
     {
         public IServiceCollection AddChannels()
         {
             services.AddSingleton<IChannelManager, ChannelManager>();
 
-            // Telegram
-            var telegramOptions = new TelegramOptions { BotToken = TelegramBotToken };
-            services.AddSingleton(telegramOptions);
-            services.AddSingleton<ITelegramBotClient>(_ => new TelegramBotClient(TelegramBotToken));
+            // Telegram — BotToken is bound from configuration ("Channels:Telegram"),
+            // supplied via the Channels__Telegram__BotToken environment variable.
+            services.AddTelegramOptions();
+            services.AddSingleton(provider => provider.GetRequiredService<IOptions<TelegramOptions>>().Value);
+            services.AddSingleton<ITelegramBotClient>(provider =>
+                new TelegramBotClient(provider.GetRequiredService<TelegramOptions>().BotToken));
             services.AddHostedService<TelegramAdapter>();
 
             return services;

Luna.Configuration/Extensions/ConfigurationBuilderExtensions.cs

@@ -34,6 +34,11 @@ public static class ConfigurationBuilderExtensions
                 builder.Add(new ProviderOptionsConfigurationSource(searchPath));
             }
 
+            // Re-applied last so environment variables take precedence over the TOML
+            // sources above. This is how secrets (API keys, bot tokens) are supplied —
+            // the embedded defaults ship with empty credentials.
+            builder.AddEnvironmentVariables();
+
             return builder;
         }
     }

Luna.Configuration/Luna.Configuration.csproj

@@ -7,6 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="10.0.5" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.5" />
     <PackageReference Include="Microsoft.Extensions.FileProviders.Embedded" Version="10.0.5" />
     <PackageReference Include="Microsoft.Extensions.Options" Version="10.0.5" />

Luna.Configuration/Resources/Providers/Provider.Mistral.toml

@@ -1,5 +1,4 @@
 
-ApiKey = "REDACTED-MISTRAL-API-KEY"
+ApiKey = ""
 ApiUrl = "https://api.mistral.ai/v1/"
 Models = ["mistral-small-latest"]
-

Luna.Configuration/Resources/Providers/Provider.Ollama.toml

@@ -1,5 +1,4 @@
 
-ApiKey = "apfelkuchen"
+ApiKey = "ollama"
 ApiUrl = "http://localhost:11434/"
 Models = ["mistral-nemo:12b"]
-