fix(server): load .env before embedded-storage worker detectio

[Teingi]

用 .env 把向量库配成 OceanBase。OceanBaseConfig 配置了 env_file=None，不会去读 .env，只靠 os.environ。结果就是启动时出现：Embedded storage detected … Forcing workers=1，把本应可用的多 worker 强行改成 1。

[Teingi]

修复方案

• 在 _is_embedded_storage() 里，先调用 _load_dotenv_if_available()，把项目 .env（或 POWERMEM_ENV_FILE 指向的文件）加载进 os.environ。
• 再构造 DatabaseSettings() 和 OceanBaseConfig()，用真实的 provider 和 是否有远程 host 来判断是否为嵌入式，从而 只在真的是 SQLite / 本地 SeekDB（host 为空）时才强制 workers=1。

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Fix

• In _is_embedded_storage(), first call _load_dotenv_if_available() to load the project .env (or the file pointed to by POWERMEM_ENV_FILE) into os.environ.
• Reconstruct DatabaseSettings() and OceanBaseConfig(), use the real provider and whether there is a remote host to determine whether it is embedded, so that workers=1 is only forced when it is really SQLite/local SeekDB (host is empty).

[Ripcord55]

Verified



Before the repair, due to a mistaken identification of oceanbase as an embedded database, the Server forced the use of "POWERMEM_SERVER_WORKERS=1" It starts in this mode, but in fact, oceanbase supports multiple workers
After the repair, when oceanbase is used as the storage database, the Server can be started normally in multi-worker mode
Simultaneously verify: pyseekdb and sqlite are normally started in the mode of "POWERMEM_SERVER_WORKERS=1"

[Evenss]

LGTM