docs: update Python 3.11 references to 3.12

- docs/quickstart.rst: bump prerequisite from 3.11 to 3.12
- CONTRIBUTING.md: bump prerequisite from 3.11 to 3.12
- docs/example/Containerfile: update comment from python-311 to python-312

Made-with: Cursor
Signed-off-by: Shanmukh Pawan <smoparth@redhat.com>

Author: smoparth

CONTRIBUTING.md

@@ -22,7 +22,7 @@ Fromager thrives on practical, well-tested contributions. This guide summarizes
 
 ### Prerequisites
 
-- Python 3.11 or newer
+- Python 3.12 or newer
 - `hatch` for environment and task management
 
   ```bash
@@ -99,7 +99,7 @@ The pre-commit hook prevents commits that would fail some CI quality checks, sav
 ### Type Annotations
 
 - Every function (including tests) must annotate all parameters and return values.
-- Use modern `X | None` syntax instead of `Optional[X]` (requires Python 3.11+).
+- Use modern `X | None` syntax instead of `Optional[X]` (PEP 604).
 - Prefer precise collection types (`list[str]`, `dict[str, int]`, etc.).
 
 ```python

docs/example/Containerfile

@@ -12,7 +12,7 @@ RUN dnf install -y --nodocs \
     patch rust cargo \
     && dnf clean all
 
-# /opt/app-root structure (same as s2i-core and ubi9/python-311)
+# /opt/app-root structure (same as s2i-core and ubi9/python-312)
 ENV APP_ROOT=/opt/app-root \
     HOME=/opt/app-root/src \
     PATH=/opt/app-root/src/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

docs/quickstart.rst

@@ -6,7 +6,7 @@ This guide gets you from zero to your first wheel build in under 5 minutes.
 Prerequisites
 -------------
 
-You'll need Python 3.11 or later and network access to download packages from PyPI.
+You'll need Python 3.12 or later and network access to download packages from PyPI.
 
 Installation
 ------------