animation du bouton sauvegarder pour se positionner en bas a droite

lib/features/analysis/analysis_screen.dart

@@ -56,6 +56,8 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
   bool _isCalibrating = false;
   bool _isSelectingReferences = false;
   bool _isFullscreenEditMode = false;
+  bool _isAtBottom = false;
+  final ScrollController _scrollController = ScrollController();
   final TransformationController _transformationController = TransformationController();
   final GlobalKey _imageKey = GlobalKey();
   double _currentZoomScale = 1.0;
@@ -64,12 +66,25 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
   void initState() {
     super.initState();
     _transformationController.addListener(_onTransformChanged);
+    _scrollController.addListener(_onScroll);
+  }
+
+  void _onScroll() {
+    if (!_scrollController.hasClients) return;
+    // Detect if we are near the bottom (within 20 pixels of the specific spacing we added)
+    final isBottom = _scrollController.position.pixels >= _scrollController.position.maxScrollExtent - 20;
+    if (isBottom != _isAtBottom) {
+      setState(() {
+        _isAtBottom = isBottom;
+      });
+    }
   }
 
   @override
   void dispose() {
     _transformationController.removeListener(_onTransformChanged);
     _transformationController.dispose();
+    _scrollController.dispose();
     super.dispose();
   }
 
@@ -160,26 +175,6 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
           }
         },
       ),
-      floatingActionButton: Consumer<AnalysisProvider>(
-        builder: (context, provider, _) {
-          if (provider.state != AnalysisState.success) return const SizedBox.shrink();
-          if (_isCalibrating) {
-            return FloatingActionButton.extended(
-              onPressed: () {
-                setState(() => _isCalibrating = false);
-              },
-              backgroundColor: AppTheme.successColor,
-              icon: const Icon(Icons.check),
-              label: const Text('Valider'),
-            );
-          }
-          return FloatingActionButton.extended(
-            onPressed: () => _saveSession(context, provider),
-            icon: const Icon(Icons.save),
-            label: const Text('Sauvegarder'),
-          );
-        },
-      ),
     );
   }
 
@@ -189,8 +184,11 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
       return _buildFullscreenEditContent(context, provider);
     }
 
-    return SingleChildScrollView(
-      child: Column(
+    return Stack(
+      children: [
+        SingleChildScrollView(
+          controller: _scrollController,
+          child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
           // Calibration mode indicator
@@ -442,9 +440,13 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
 
                   // Action buttons
                   _buildActionButtons(context, provider),
+
+                  // Large spacing at the bottom to trigger the state change
+                  const SizedBox(height: 100),
                 ],
               ),
             )
+
           else
             // Calibration info
             Padding(
@@ -498,7 +500,74 @@ class _AnalysisScreenContentState extends State<_AnalysisScreenContent> {
             ),
         ],
       ),
-    );
+    ),
+      Positioned(
+        bottom: 0,
+        left: 0,
+        right: 0,
+        child: Align(
+          alignment: _isAtBottom ? Alignment.bottomCenter : Alignment.bottomRight,
+          child: Padding(
+            padding: _isAtBottom ? EdgeInsets.zero : const EdgeInsets.all(16.0),
+            child: _isCalibrating 
+            ? FloatingActionButton.extended(
+                onPressed: () => setState(() => _isCalibrating = false),
+                backgroundColor: AppTheme.successColor,
+                icon: const Icon(Icons.check),
+                label: const Text('Valider'),
+              )
+            : AnimatedContainer(
+                duration: const Duration(milliseconds: 260),
+                curve: Curves.easeInOut,
+                width: _isAtBottom ? MediaQuery.of(context).size.width : 180,
+                height: 56,
+                decoration: BoxDecoration(
+                  color: AppTheme.primaryColor,
+                  borderRadius: BorderRadius.circular(_isAtBottom ? 0 : 16),
+                  boxShadow: [
+                    if (!_isAtBottom) 
+                      BoxShadow(
+                        color: Colors.black.withOpacity(0.2),
+                        blurRadius: 6,
+                        offset: const Offset(0, 3),
+                      ),
+                  ],
+                ),
+                child: Material(
+                  color: Colors.transparent,
+                  child: InkWell(
+                    onTap: () => _saveSession(context, provider),
+                    borderRadius: BorderRadius.circular(_isAtBottom ? 0 : 16),
+                    child: Padding(
+                      padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 16),
+                      child: FittedBox(
+                        fit: BoxFit.scaleDown,
+                        child: Row(
+                        mainAxisSize: MainAxisSize.min,
+                        mainAxisAlignment: MainAxisAlignment.center,
+                        children: [
+                          const Icon(Icons.save, color: Colors.white),
+                          const SizedBox(width: 8),
+                          Text(
+                            _isAtBottom ? 'SAUVEGARDER LA SESSION' : 'Sauvegarder',
+                            style: const TextStyle(
+                              color: Colors.white, 
+                              fontWeight: FontWeight.bold,
+                              fontSize: 16
+                            ),
+                          ),
+                        ],
+                      ),
+                      ),
+                    ),
+                  ),
+                ),
+            ),
+          ),
+        ),
+      ),
+    ],
+  );
   }
 
   Widget _buildZoomableImageWithOverlay(BuildContext context, AnalysisProvider provider) {