refactor(#82): remove dead SkeletonList/SkeletonCard composables

* ci: prevent concurrency cancellation on rapid main merges

The concurrency group used github.ref which is static for main
(refs/heads/main). When multiple PRs merged rapidly (~2 min apart),
each merge commit cancelled the previous CI run before it could finish.

Fix: use github.sha for push events to main (unique per commit) while
keeping the ref-based group for PR branches (cancels on new commits to
the same PR branch).

* refactor(#82): remove dead SkeletonList/SkeletonCard composables

---------

Co-authored-by: ronia <ronia@m57>
Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/ui/common/StateViews.kt

@@ -1,24 +1,14 @@
 package com.m57.hermescontrol.ui.common
 
-import androidx.compose.animation.core.RepeatMode
-import androidx.compose.animation.core.animateFloat
-import androidx.compose.animation.core.infiniteRepeatable
-import androidx.compose.animation.core.rememberInfiniteTransition
-import androidx.compose.animation.core.tween
-import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.width
-import androidx.compose.foundation.lazy.LazyColumn
-import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Inbox
 import androidx.compose.material.icons.filled.Refresh
@@ -29,16 +19,12 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clip
-import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import com.m57.hermescontrol.theme.LocalSpacing
-import com.m57.hermescontrol.theme.Motion
 
 // Unified loading / error / empty / skeleton placeholders so every screen
 // shares the same visual language.
@@ -59,74 +45,6 @@ fun LoadingState(modifier: Modifier = Modifier) {
     }
 }
 
-// ── Skeleton Shimmer ──────────────────────────────────────────────────
-
-/**
- * Shimmer placeholder for list-based loading states.
- * Shows animated placeholder cards while real data loads.
- *
- * @param itemCount number of skeleton rows to show
- */
-@Composable
-fun SkeletonList(
-    itemCount: Int = 6,
-    modifier: Modifier = Modifier,
-) {
-    val spacing = LocalSpacing.current
-    val infiniteTransition = rememberInfiniteTransition(label = "shimmer")
-    val shimmerAlpha by infiniteTransition.animateFloat(
-        initialValue = 0.3f,
-        targetValue = 0.7f,
-        animationSpec =
-            infiniteRepeatable(
-                animation = tween(Motion.NORMAL * 2),
-                repeatMode = RepeatMode.Reverse,
-            ),
-        label = "shimmerAlpha",
-    )
-    val skeletonColor = MaterialTheme.colorScheme.surfaceVariant.copy(alpha = shimmerAlpha)
-
-    LazyColumn(
-        modifier = modifier.fillMaxSize(),
-        contentPadding = PaddingValues(horizontal = spacing.md, vertical = spacing.sm),
-        verticalArrangement = Arrangement.spacedBy(spacing.sm),
-    ) {
-        items(itemCount) {
-            SkeletonCard(skeletonColor)
-        }
-    }
-}
-
-@Composable
-private fun SkeletonCard(baseColor: Color) {
-    Column(
-        modifier =
-            Modifier
-                .fillMaxWidth()
-                .clip(RoundedCornerShape(12.dp))
-                .background(baseColor)
-                .padding(16.dp),
-    ) {
-        Box(
-            modifier =
-                Modifier
-                    .width(180.dp)
-                    .height(16.dp)
-                    .clip(RoundedCornerShape(4.dp))
-                    .background(baseColor.copy(alpha = baseColor.alpha + 0.1f)),
-        )
-        Spacer(modifier = Modifier.height(8.dp))
-        Box(
-            modifier =
-                Modifier
-                    .fillMaxWidth(0.7f)
-                    .height(12.dp)
-                    .clip(RoundedCornerShape(4.dp))
-                    .background(baseColor.copy(alpha = baseColor.alpha + 0.05f)),
-        )
-    }
-}
-
 // ── Error ──────────────────────────────────────────────────────────────
 
 @Composable