Add Luna.Configuration with TOML-based agent and provider config

Implement configuration system with embedded TOML resources for agent
and provider definitions, custom IConfigurationSource/Provider for
agent and provider options, and DI extension methods. Includes config
models for agents, providers, sessions, and Telegram integration.

Luna.Configuration/Resources/Agents/Agent.Core.toml

@@ -0,0 +1,19 @@
+
+Name = "Core"
+Description = '''
+The Core Agent is responsible for managing the overall system and coordinating the actions of other agents.
+'''
+Provider = "Mistral"
+ModelId = "mistral-large-latest"
+MaxContextTokens = 256_000
+Instructions = '''
+## L.U.N.A. (Lovely Unit for Nerdy Assistance)
+
+You are Luna, an AI personal assistant.
+
+# Core Identity
+
+* Role: Personal assistance, researcher or co-programmer
+* Personality: Calm, witty, organized, supportive
+* Communication: Concise, structured, encouraging 
+'''

Luna.Configuration/Resources/Agents/Agent.Librarian.toml

@@ -0,0 +1,13 @@
+
+Name = "Librarian"
+Description = '''
+The Librarian Agent is responsible for summarizing and condensing the conversation history into concise context for future interactions.
+'''
+Provider = "Mistral"
+ModelId = "mistral-small-latest"
+MaxContextTokens = 256_000
+Instructions = '''
+You are a conversation compaction engine.
+Summarize older chat history into concise context for future turns.
+Preserve: user preferences, commitments, decisions, unresolved tasks, key facts, file paths, and identifiers. Omit: filler, repeated chit-chat, verbose tool logs. Output plain text bullet points only.
+'''

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

@@ -0,0 +1,5 @@
+
+ApiKey = "REDACTED-MISTRAL-API-KEY"
+ApiUrl = "https://api.mistral.ai/v1/"
+Models = ["mistral-small-latest"]
+

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

@@ -0,0 +1,5 @@
+
+ApiKey = "apfelkuchen"
+ApiUrl = "http://localhost:11434/"
+Models = ["mistral-nemo:12b"]
+