refactor(vectordb): remove legacy vectorize path

[qin-ctx]

Description

移除底层 vectordb collection 的遗留 Vectorize 自动向量化路径，避免它和 OpenViking 当前标准 embedding queue 链路混淆。标准链路中的 openviking.core.context.Vectorize 和 embedding.max_input_tokens 处理不受影响。

Related Issue

无直接关闭 issue。背景来自 #3010 排查，但本 PR 不关闭该 issue。

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• 删除 openviking/storage/vectordb/vectorize/ 下的旧自动向量化实现。
• LocalCollection 不再创建或持有 VectorizerAdapter，写入时只接受调用方传入的 vector / sparse_vector。
• collection create API 和 metadata validation 不再暴露 Vectorize 配置，并在 CollectionMeta 构建时丢弃历史传入的 Vectorize 字段。

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

本地验证：

• python3 -m py_compile openviking/storage/vectordb/collection/local_collection.py openviking/storage/vectordb/meta/collection_meta.py openviking/storage/vectordb/service/api_fastapi.py openviking/storage/vectordb/service/app_models.py openviking/storage/vectordb/utils/validation.py
• git diff --check
• rg -n "VectorizerAdapter|VectorizerFactory|BaseVectorizer|openviking\\.storage\\.vectordb\\.vectorize|meta\\.vectorize|request\\.Vectorize|\\\"Vectorize\\\"|Vectorize:" openviking tests -S

未运行：当前环境缺少 pytest 和 ruff Python 模块。

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

不适用。

Additional Notes

这个 PR 只清理底层 vectordb collection meta 的 Vectorize 自动向量化能力；不删除主链路使用的 openviking.core.context.Vectorize 数据结构。