Refactor Agent Orchestrator

[pravin-python]

Refactored the WorkSynapse LangChain orchestrator into a dynamic, modular, and testable architecture.

Key changes:

• Created a new directory structure under backend/app/agents/: runtime, orchestrator, providers, tools, rag, memory, prompts, testing.
• Implemented ProviderRouter for dynamic LLM provider selection.
• Implemented PromptBuilder for dynamic prompt construction from templates and database.
• Implemented ExecutionLoop using LangGraph with proper state management (Annotated[list, add_messages]) and MCP tool support.
• Implemented AgentOrchestrator with security checks and memory integration.
• Implemented AgentRuntime to handle agent execution requests, fetching configurations and permissions from the database.
• Refactored Tools and Memory into modular components.
• Refactored RAG into Retriever, EmbeddingService, and DocumentLoader.
• Added a testing framework with AgentTester, ToolTester, and ProviderTester.
• Updated existing imports and cleaned up old files.
• Added missing test fixtures and fixed backend tests.

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PR created automatically by Jules for task 13252202557393851395 started by @pravin-python

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