fix: revert marshmallow to 3.x (4.x breaks schemas)

Marshmallow 4.x removed the `missing` keyword argument (renamed to
`load_default`), breaking all schema definitions in restx_api/schemas.py.
Revert to 3.26.2 for compatibility.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: marketcalls

pyproject.toml

@@ -71,7 +71,7 @@ dependencies = [
   "logzero==1.7.0",
   "markdown-it-py==4.0.0",
   "MarkupSafe==2.1.5",
-  "marshmallow==4.2.2",
+  "marshmallow==3.26.2",
   "matplotlib-inline==0.2.1",
   "mcp==1.26.0",
   "mdurl==0.1.2",

requirements-nginx.txt

@@ -65,7 +65,7 @@ logistro==2.0.1
 logzero==1.7.0
 markdown-it-py==4.0.0
 MarkupSafe==2.1.5
-marshmallow==4.2.2
+marshmallow==3.26.2
 matplotlib-inline==0.2.1
 mcp==1.26.0
 mdurl==0.1.2

requirements.txt

@@ -65,7 +65,7 @@ logistro==2.0.1
 logzero==1.7.0
 markdown-it-py==4.0.0
 MarkupSafe==2.1.5
-marshmallow==4.2.2
+marshmallow==3.26.2
 matplotlib-inline==0.2.1
 mcp==1.26.0
 mdurl==0.1.2