fix(api): Pydantic-settings for model-based env loading

src/api/uv.lock

@@ -191,6 +191,7 @@ dependencies = [
     { name = "aiohttp-client-cache", extra = ["all"] },
     { name = "ebooklib" },
     { name = "fastapi" },
+    { name = "pydantic-settings" },
     { name = "python-dotenv" },
     { name = "rich" },
 ]
@@ -201,6 +202,7 @@ requires-dist = [
     { name = "aiohttp-client-cache", extras = ["all"], specifier = ">=0.10.0" },
     { name = "ebooklib", specifier = ">=0.18" },
     { name = "fastapi", specifier = ">=0.115.5" },
+    { name = "pydantic-settings", specifier = ">=2.6.1" },
     { name = "python-dotenv", specifier = ">=1.0.1" },
     { name = "rich", specifier = ">=13.9.4" },
 ]
@@ -616,6 +618,19 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/33/72/f881b5e18fbb67cf2fb4ab253660de3c6899dbb2dba409d0b757e3559e3d/pydantic_core-2.27.1-pp310-pypy310_pp73-win_amd64.whl", hash = "sha256:981fb88516bd1ae8b0cbbd2034678a39dedc98752f264ac9bc5839d3923fa04c", size = 2001864 },
 ]
 
+[[package]]
+name = "pydantic-settings"
+version = "2.6.1"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pydantic" },
+    { name = "python-dotenv" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/b5/d4/9dfbe238f45ad8b168f5c96ee49a3df0598ce18a0795a983b419949ce65b/pydantic_settings-2.6.1.tar.gz", hash = "sha256:e0f92546d8a9923cb8941689abf85d6601a8c19a23e97a34b2964a2e3f813ca0", size = 75646 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/5e/f9/ff95fd7d760af42f647ea87f9b8a383d891cdb5e5dbd4613edaeb094252a/pydantic_settings-2.6.1-py3-none-any.whl", hash = "sha256:7fb0637c786a558d3103436278a7c4f1cfd29ba8973238a50c5bb9a55387da87", size = 28595 },
+]
+
 [[package]]
 name = "pygments"
 version = "2.18.0"