beamer: resizebox table filter + org-beamer-frame-default-options

- org-beamer-frame-default-options = allowframebreaks (proper way,
  not renewenvironment frame hack which caused empty slides)
- my/org-beamer-resizebox-tables: export filter wraps tabular in
  resizebox{textwidth}{!} for beamer backend only
- document.org export unchanged (still uses tabularx filter)

config.el

@@ -412,6 +412,29 @@ Skip for beamer exports — beamer uses adjustbox wrapper on plain tabular inste
 
 (add-hook 'org-export-before-processing-hook #'my/org-ensure-tabularx-filter)
 
+;; Beamer: tables → resizebox (scale to slide width), allowframebreaks globally
+(with-eval-after-load 'ox-beamer
+  (setq org-beamer-frame-default-options "allowframebreaks"))
+
+(defun my/org-beamer-resizebox-tables (table backend _info)
+  "Wrap tabular environments in \\resizebox for beamer exports."
+  (when (and (stringp table)
+             (org-export-derived-backend-p backend 'beamer))
+    (with-temp-buffer
+      (insert table)
+      (goto-char (point-min))
+      (when (re-search-forward "\\\\begin{tabular}" nil t)
+        (goto-char (match-beginning 0))
+        (insert "\\resizebox{\\textwidth}{!}{%\n")
+        (goto-char (point-max))
+        (when (search-backward "\\end{tabular}" nil t)
+          (goto-char (match-end 0))
+          (insert "\n}")))
+      (buffer-string))))
+
+(with-eval-after-load 'ox-beamer
+  (add-to-list 'org-export-filter-table-functions #'my/org-beamer-resizebox-tables))
+
 ;; Optional: enable booktabs style (horizontal rules in tables)
 ;; (setq org-latex-tables-booktabs t)