fix(execution): carrousel de médias et chrono du score (tickets #41, #42, #43)

Corrige l'affichage des images (#41) et de la vidéo (#42) dans le
carrousel de médias, et le format du chrono de score qui n'affichait
que les secondes (#43) sur workout_execution_screen.dart. Ajoute la
dépendance video_player (2.13.0) pour la lecture vidéo. Ajuste
home_screen.dart, history_screen.dart et workout_template_screen.dart
en conséquence. flutter analyze propre, flutter test 77/77 vert (plus
aucun hang), pub get résolu.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pubspec.lock

@@ -177,6 +177,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.7"
+  csslib:
+    dependency: transitive
+    description:
+      name: csslib
+      sha256: "09bad715f418841f976c77db72d5398dc1253c21fb9c0c7f0b0b985860b2d58e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.2"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -344,6 +352,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.2"
+  html:
+    dependency: transitive
+    description:
+      name: html
+      sha256: "6d1264f2dffa1b1101c25a91dff0dc2daee4c18e87cd8538729773c073dbf602"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.15.6"
   http:
     dependency: transitive
     description:
@@ -829,6 +845,46 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.2.0"
+  video_player:
+    dependency: "direct main"
+    description:
+      name: video_player
+      sha256: "20ef311160e2ced020a62f38e4cc399a1bf289e722fc5fe37c9d7b18e44c9e8d"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.13.0"
+  video_player_android:
+    dependency: transitive
+    description:
+      name: video_player_android
+      sha256: "5121de08444d00363efdda630a69ad4d27a208a9f7586482d4909a44a1cdbc63"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.11.0"
+  video_player_avfoundation:
+    dependency: transitive
+    description:
+      name: video_player_avfoundation
+      sha256: c238f5f0a26845cd0bcc2956049b63065a4d3c40ddfc22c3414cd170bef7fff9
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.11.0"
+  video_player_platform_interface:
+    dependency: transitive
+    description:
+      name: video_player_platform_interface
+      sha256: "92c0fbabe20c788e71fd10d26cea998d0d253282e65d145aed0818731cf593ce"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.9.0"
+  video_player_web:
+    dependency: transitive
+    description:
+      name: video_player_web
+      sha256: "9f3c00be2ef9b76a95d94ac5119fb843dca6f2c69e6c9968f6f2b6c9e7afbdeb"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.4.0"
   vm_service:
     dependency: transitive
     description: