v1.3.0: Refactoring Phase 3+4, Symbol-Verwaltung Redesign, Schlauch-Labels Fix

- Refactoring: Error Boundaries, apiFetch Wrapper, Socket Status-Tracking
- Refactoring: UI Kontrast (theme-aware colors), unused imports bereinigt
- Symbol-Verwaltung: Neues Split-Panel (Meine Symbole + Bibliothek)
- Symbol-Verwaltung: Umbenennen (TLF rot/blau), Duplikate erlaubt
- Symbol-Verwaltung: Karten-Sidebar zeigt eigene Symbole bevorzugt
- Schlauch-Labels: Groessere Schrift (13px/10px), verschiebbar (Drag)
- Schema: TenantSymbol customName, sortOrder, unique constraint entfernt
- Open Source Referenz entfernt (kostenloses Projekt)

prisma/schema.prisma

@@ -378,11 +378,13 @@ model UpgradeRequest {
   @@map("upgrade_requests")
 }
 
-// ─── Tenant Symbol Visibility ─────────────────────────────
+// ─── Tenant Symbol Collection ─────────────────────────────
 
 model TenantSymbol {
-  id       String  @id @default(uuid())
-  isActive Boolean @default(true)
+  id         String   @id @default(uuid())
+  customName String?
+  sortOrder  Int      @default(0)
+  createdAt  DateTime @default(now())
 
   tenantId String
   tenant   Tenant @relation(fields: [tenantId], references: [id], onDelete: Cascade)
@@ -390,7 +392,7 @@ model TenantSymbol {
   iconId String
   icon   IconAsset @relation(fields: [iconId], references: [id], onDelete: Cascade)
 
-  @@unique([tenantId, iconId])
+  @@index([tenantId])
   @@map("tenant_symbols")
 }