Android overhaul: shared failure texts, saved-split label and limits in :core:design

* format/Failures.kt: FAILURE_NETWORK and commonFailureText, the §14.3.2 code-to-text map that :feature:account
  (Errors.kt) and :feature:settings (Messages.kt) each spelled out; both keep only their own codes. The "network"
  literals in :feature:onboarding and the two NETWORK constants use FAILURE_NETWORK.
* component/Split.kt: savedSplitLabel, the S-8 and S-16 line ("Kontots standard 50/50", "Egen fördelning 70/30",
  "Exakta belopp", "Allt på dig/Anna") that ExpenseDetailScreen.modeLabel and SyncStatusScreen.lostModeLabel
  duplicated line for line.
* format/Limits.kt: BP_TOTAL (five copies in four features and a literal in :core:design and S-19) and
  DISPLAY_NAME_MAX (three copies in :feature:onboarding and :feature:settings).

Behaviour and goldens unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

android/core/design/src/main/kotlin/se/hagstedt/kvitt/design/component/Split.kt

@@ -48,6 +48,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.withStyle
 import se.hagstedt.kvitt.core.design.R
 import se.hagstedt.kvitt.design.KvittTheme
+import se.hagstedt.kvitt.design.format.BP_TOTAL
 import se.hagstedt.kvitt.design.format.MoneyFormatter
 import se.hagstedt.kvitt.design.icon.KvittIcon
 import se.hagstedt.kvitt.design.theme.KvittDimens
@@ -113,7 +114,7 @@ fun ratioSpoken(left: User, leftBp: Int, right: User): String {
         personName(left),
         MoneyFormatter.basisPoints(leftBp, language),
         personName(right),
-        MoneyFormatter.basisPoints(10_000 - leftBp, language),
+        MoneyFormatter.basisPoints(BP_TOTAL - leftBp, language),
     )
 }
 
@@ -202,6 +203,29 @@ fun splitModeLabel(mode: SplitMode, defaultLabel: String): String = when (mode)
 fun defaultModeLabel(viewerPercent: Int): String =
     stringResource(R.string.editor_split_mode_default, stringResource(R.string.common_ratio, viewerPercent.toString(), (100 - viewerPercent).toString()))
 
+/**
+ * A saved split as one line (design-spec S-8, S-16): "Kontots standard 50/50" or "Egen fördelning 70/30" with the
+ * [viewer]'s basis points from [shares] (50/50 for a default split without them), "Exakta belopp", or "Allt på dig" /
+ * "Allt på <[partnerName]>" by who bears the amount.
+ */
+@Composable
+fun savedSplitLabel(mode: SplitMode, shares: List<Share>, viewer: UserId, partnerName: String): String {
+    val language = kvittLanguage()
+    val mineBp = shares.firstOrNull { it.userId == viewer }?.shareBp
+    val ratio = mineBp?.let { stringResource(R.string.common_ratio, MoneyFormatter.basisPoints(it, language), MoneyFormatter.basisPoints(BP_TOTAL - it, language)) }
+    return when (mode) {
+        SplitMode.DEFAULT -> if (ratio != null) stringResource(R.string.editor_split_mode_default, ratio) else defaultModeLabel(HALF_PERCENT)
+        SplitMode.RATIO -> splitModeLabel(mode, "") + (ratio?.let { " $it" } ?: "")
+        SplitMode.EXACT -> splitModeLabel(mode, "")
+        SplitMode.FULL -> {
+            val bearer = shares.firstOrNull { it.shareOre > 0 }?.userId
+            if (bearer == viewer) stringResource(R.string.editor_split_full_on_you) else stringResource(R.string.editor_split_full_on, partnerName)
+        }
+    }
+}
+
+private const val HALF_PERCENT = 50
+
 /**
  * The open split section (design-spec §3.7): a flat section with the header "Delning" and a collapse button, the four
  * mode chips as a radio group, then [body]: the split bar and preview for `default`, or [RatioEditor],
@@ -474,4 +498,3 @@ fun viewerPercentOf(defaultShares: Map<UserId, Int>, viewer: UserId): Int = (def
 
 private const val HALF_BP = 5_000
 private const val BP_PER_PERCENT = 100
-

android/core/design/src/main/kotlin/se/hagstedt/kvitt/design/format/Failures.kt

@@ -0,0 +1,25 @@
+package se.hagstedt.kvitt.design.format
+
+import androidx.annotation.StringRes
+import se.hagstedt.kvitt.core.design.R
+
+/** The code of an online call that did not reach the server: `OnlineResult.Failed("network", null)` (D-029). */
+const val FAILURE_NETWORK = "network"
+
+/**
+ * The shared snackbar text of a refused online call (design-spec §1, `strings.csv` `error_*`) for the codes every
+ * screen can meet: [FAILURE_NETWORK] is "Kunde inte nå servern", the §14.3.2 codes their text. Null for any other code,
+ * which the screen maps itself (falling back to `error_generic_invalid`).
+ */
+@StringRes
+fun commonFailureText(code: String): Int? = when (code) {
+    FAILURE_NETWORK -> R.string.common_could_not_reach_server
+    "household_incomplete" -> R.string.error_household_incomplete
+    "not_found" -> R.string.error_not_found
+    "forbidden" -> R.string.error_forbidden
+    "rate_limited" -> R.string.error_rate_limited
+    "protocol_unsupported" -> R.string.error_app_too_old
+    "internal", "unavailable", "not_implemented" -> R.string.error_server
+    "validation_failed" -> R.string.error_validation
+    else -> null
+}

android/core/design/src/main/kotlin/se/hagstedt/kvitt/design/format/Limits.kt

@@ -0,0 +1,7 @@
+package se.hagstedt.kvitt.design.format
+
+/** Basis points of a whole: a ratio's per-user shares sum to 10000 bp, 100 % (SPEC §1, §9.3). */
+const val BP_TOTAL = 10_000
+
+/** A user's display name is 1 to 40 code points after trimming (SPEC §9.6). */
+const val DISPLAY_NAME_MAX = 40