fix(dashboard): diagrammes BPMN/DFG grande taille (DPI 150, layout vertical)

Les images générées par PM4Py étaient trop petites et illisibles.
- DPI 150, taille 40x20 pouces, layout vertical (TB)
- La modale plein écran permet le défilement (scroll)
- Fallback sur pm4py.save_vis si le rendu Graphviz échoue

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

core/analytics/process_mining_bridge.py

@@ -391,26 +391,48 @@ def discover_bpmn(
         bpmn_exporter.apply(bpmn_model, bpmn_xml_path)
     logger.info("BPMN XML exporte : %s", bpmn_xml_path)
 
-    # Export image BPMN (PNG)
+    # Export image BPMN (PNG) — grande taille pour lisibilité
     bpmn_image_path = str(out / f"{name}_bpmn.png")
     try:
-        pm4py.save_vis_bpmn(bpmn_model, bpmn_image_path)
+        from pm4py.visualization.bpmn import visualizer as bpmn_vis
+        gviz = bpmn_vis.apply(bpmn_model, parameters={
+            "rankdir": "TB",
+            "font_size": "12",
+        })
+        gviz.graph_attr["dpi"] = "150"
+        gviz.graph_attr["size"] = "40,20!"
+        gviz.graph_attr["rankdir"] = "TB"
+        gviz.render(filename=bpmn_image_path.replace(".png", ""), format="png", cleanup=True)
         logger.info("BPMN PNG exporte : %s", bpmn_image_path)
     except Exception as e:
-        logger.warning("Impossible de generer l'image BPMN : %s", e)
-        bpmn_image_path = None
+        logger.warning("BPMN image fallback : %s", e)
+        try:
+            pm4py.save_vis_bpmn(bpmn_model, bpmn_image_path)
+        except Exception:
+            bpmn_image_path = None
 
-    # DFG (Directly-Follows Graph) avec performance
+    # DFG (Directly-Follows Graph) — grande taille
     dfg_image_path = str(out / f"{name}_dfg.png")
     try:
-        pm4py.save_vis_dfg(
-            *pm4py.discover_dfg(event_log_df),
-            file_path=dfg_image_path,
-        )
+        from pm4py.visualization.dfg import visualizer as dfg_vis
+        dfg, sa, ea = pm4py.discover_dfg(event_log_df)
+        gviz = dfg_vis.apply(dfg, activities_count=sa, parameters={
+            "start_activities": sa,
+            "end_activities": ea,
+            "rankdir": "TB",
+            "font_size": "11",
+        })
+        gviz.graph_attr["dpi"] = "150"
+        gviz.graph_attr["size"] = "40,20!"
+        gviz.graph_attr["rankdir"] = "TB"
+        gviz.render(filename=dfg_image_path.replace(".png", ""), format="png", cleanup=True)
         logger.info("DFG PNG exporte : %s", dfg_image_path)
     except Exception as e:
-        logger.warning("Impossible de generer le DFG : %s", e)
-        dfg_image_path = None
+        logger.warning("DFG image fallback : %s", e)
+        try:
+            pm4py.save_vis_dfg(*pm4py.discover_dfg(event_log_df), file_path=dfg_image_path)
+        except Exception:
+            dfg_image_path = None
 
     # Petri net via Inductive Miner (pour visualisation alternative)
     petri_image_path = str(out / f"{name}_petri.png")