refactor: Extract manager setup logic into modular providers

[HyeockJinKim]

Moved dependency initialization and configuration code from server.py into separate provider modules under providers/ directory for better separation of concerns and maintainability.

Each provider module handles a specific aspect of manager setup:

• Database connections and models
• Redis clients (image, live, stat, stream, etc.)
• Event system (dispatcher, producer, hub)
• Background tasks and message queues
• Service discovery and leader election
• Plugin systems (event dispatcher, hooks, network)
• Monitoring and idle checking
• Core repositories and services
• Sokovan orchestrator

resolves #3931 (BA-938)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[Copilot]

Pull Request Overview

This PR refactors the manager initialization logic by extracting dependency setup code from a monolithic server.py file into modular provider modules under the providers/ directory. This improves separation of concerns and maintainability by organizing related setup logic into focused modules.

Key changes:

• Extracted context manager functions from server.py into 22 dedicated provider modules
• Each provider handles initialization of specific manager subsystems (database, Redis, events, etc.)
• Reduced the size of server.py by ~750 lines while preserving existing functionality
• Added proper imports for all extracted providers in server.py

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

File	Description
src/ai/backend/manager/server.py	Removed inline context managers and replaced with imports from provider modules
src/ai/backend/manager/providers/__init__.py	Added package initialization with module description
src/ai/backend/manager/providers/*.py	22 new provider modules, each handling specific aspect of manager setup (database, Redis, events, etc.)

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[Copilot]

Import path inconsistency: other provider modules use from ai.backend.logging import BraceStyleAdapter while this module uses from ai.backend.logging.utils import BraceStyleAdapter. Should be consistent across all provider modules.

Suggested change

	from ai.backend.logging.utils import BraceStyleAdapter
	from ai.backend.logging import BraceStyleAdapter

[Copilot]

Missing cleanup logic in the storage manager context. The original code had await root_ctx.storage_manager.aclose() in the finally block, but this extracted version only has yield without proper cleanup.

Suggested change

	yield
	try:
	yield
	finally:
	await root_ctx.storage_manager.aclose()