feat(BA-2847): Add base class for minilang filter and ordering converter implementations

[seedspirit]

resolves #6429 (BA-2847)

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 introduces two new abstract base classes for converting minilang expressions to domain-specific objects: BaseMinilangFilterConverter for filter expressions and BaseMinilangOrderParser for order expressions. These base classes provide reusable parsing and conversion logic that can be extended by domain-specific implementations.

• Adds BaseMinilangFilterConverter to convert minilang filter expressions to structured Filter objects with support for AND/OR logical operations
• Adds BaseMinilangOrderParser to parse order expressions (e.g., "+id,-status") into OrderingOption objects
• Introduces two new exception classes: InvalidParameter and ASTParsingFailed for better error handling

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/ai/backend/manager/repositories/types.py	Adds BaseMinilangFilterConverter and BaseMinilangOrderParser abstract base classes with supporting methods for parsing and converting minilang expressions
src/ai/backend/common/exception.py	Adds InvalidParameter and ASTParsingFailed exception classes for parameter validation and AST parsing errors
changes/6492.feature.md	Documents the feature addition for the changelog

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