[INT-001] integration: Fix API response format inconsistencies

- Fixed nested response structures in profile_handler.go (3 occurrences)
- Fixed nested response structures in playlist_handler.go (4 occurrences)
- Changed gin.H{"profile": profile} to profile directly
- Changed gin.H{"playlist": playlist} to playlist directly
- Changed gin.H{"collaborator": collaborator} to collaborator directly
- All responses now use consistent { success: true, data: {...} } format
- Frontend interceptor already handles unwrapping correctly

Phase: PHASE-1
Priority: P0
Progress: 6/267 (2.2%)

VEZA_COMPLETE_MVP_TODOLIST.json

@@ -690,7 +690,7 @@
       "completion": {
         "completed_at": "2025-12-23T00:41:32Z",
         "actual_hours": 1.0,
-        "commits": [],
+        "commits": ["ed8949ee76acabe3aba59860f4f757f577b60cba"],
         "files_changed": [
           "veza-backend-api/internal/api/router.go",
           "veza-backend-api/internal/handlers/playlist_handler.go"
@@ -772,7 +772,18 @@
       "description": "Backend returns { success, data } but some handlers return nested structures (e.g., { profile: {...} }) while frontend expects flat data. Standardize all responses.",
       "owner": "fullstack",
       "estimated_hours": 4,
-      "status": "todo",
+      "status": "completed",
+      "completion": {
+        "completed_at": "2025-12-23T00:42:45Z",
+        "actual_hours": 1.0,
+        "commits": [],
+        "files_changed": [
+          "veza-backend-api/internal/handlers/profile_handler.go",
+          "veza-backend-api/internal/handlers/playlist_handler.go"
+        ],
+        "notes": "Fixed nested response structures in handlers. Changed gin.H{\"profile\": profile} to profile (3 occurrences in profile_handler.go). Changed gin.H{\"playlist\": playlist} to playlist (3 occurrences in playlist_handler.go). Changed gin.H{\"collaborator\": collaborator} to collaborator (1 occurrence in playlist_handler.go). Frontend already has interceptor that unwraps { success, data } format correctly. All responses now use consistent { success: true, data: {...} } format where data contains the object directly, not nested in a key.",
+        "issues_encountered": []
+      },
       "files_involved": [
         {
           "path": "veza-backend-api/internal/handlers/profile_handler.go",

veza-backend-api/internal/handlers/playlist_handler.go

@@ -109,7 +109,7 @@ func (h *PlaylistHandler) CreatePlaylist(c *gin.Context) {
 	// MOD-P2-003: Enregistrer la métrique business (depuis le handler pour éviter cycle d'import)
 	monitoring.RecordPlaylistCreated()
 
-	RespondSuccess(c, http.StatusCreated, gin.H{"playlist": playlist})
+	RespondSuccess(c, http.StatusCreated, playlist)
 }
 
 // GetPlaylists gère la récupération des playlists avec pagination
@@ -220,7 +220,7 @@ func (h *PlaylistHandler) GetPlaylist(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusOK, gin.H{"playlist": playlist})
+	RespondSuccess(c, http.StatusOK, playlist)
 }
 
 // UpdatePlaylist gère la mise à jour d'une playlist
@@ -277,7 +277,7 @@ func (h *PlaylistHandler) UpdatePlaylist(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusOK, gin.H{"playlist": playlist})
+	RespondSuccess(c, http.StatusOK, playlist)
 }
 
 // DeletePlaylist gère la suppression d'une playlist
@@ -575,7 +575,7 @@ func (h *PlaylistHandler) AddCollaborator(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusCreated, gin.H{"collaborator": collaborator})
+	RespondSuccess(c, http.StatusCreated, collaborator)
 }
 
 // RemoveCollaborator gère la suppression d'un collaborateur d'une playlist

veza-backend-api/internal/handlers/profile_handler.go

@@ -68,7 +68,7 @@ func (h *ProfileHandler) GetProfile(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusOK, gin.H{"profile": profile})
+	RespondSuccess(c, http.StatusOK, profile)
 }
 
 // GetProfileByUsername retrieves a public profile by username
@@ -104,7 +104,7 @@ func (h *ProfileHandler) GetProfileByUsername(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusOK, gin.H{"profile": profile})
+	RespondSuccess(c, http.StatusOK, profile)
 }
 
 // GetProfileCompletion retrieves the profile completion status
@@ -291,7 +291,7 @@ func (h *ProfileHandler) UpdateProfile(c *gin.Context) {
 		return
 	}
 
-	RespondSuccess(c, http.StatusOK, gin.H{"profile": profile})
+	RespondSuccess(c, http.StatusOK, profile)
 }
 
 // isValidUsername validates username format (alphanumeric + underscore, 3-30 chars)