fix: pin black to 26.3.1 across all environments

- Pin black version in requirements-dev.txt (was >=24.0.0)
- Update pre-commit to use black 26.3.1 with Python 3.12
- Add language_version: python3.12 to pre-commit black hook
- Reformat files with new black version for consistency

app/pages/overview.py

@@ -124,13 +124,11 @@ def welcome_page(request: Request):
                     if turnstile.uses_test_keys
                     else ""
                 )
-                ui.html(
-                    f"""<form method="post" action="/workspaces/bootstrap" class="flex items-center gap-4">
+                ui.html(f"""<form method="post" action="/workspaces/bootstrap" class="flex items-center gap-4">
                         {hidden_token}
                         <div class="cf-turnstile" data-sitekey="{turnstile.site_key}"></div>
                         <button type="submit" class="rounded-lg bg-slate-900 px-5 py-3 text-sm font-semibold text-white no-underline dark:bg-slate-100 dark:text-slate-900">Get started</button>
-                    </form>"""
-                )
+                    </form>""")
                 ui.label("You can always create a fresh workspace later if a link is lost.").classes(
                     "text-sm text-slate-500 dark:text-slate-400"
                 )