Add comprehensive i18n localization for KMM and iOS

KMM (Android/Shared):
- Add strings.xml with 200+ localized strings
- Add translation files for es, fr, de, pt languages
- Update all screens to use stringResource() for i18n
- Add Accept-Language header to API client for all platforms

iOS:
- Add L10n.swift helper with type-safe string accessors
- Add Localizable.xcstrings with translations for all 5 languages
- Update all SwiftUI views to use L10n.* for localized strings
- Localize Auth, Residence, Task, Contractor, Document, and Profile views

Supported languages: English, Spanish, French, German, Portuguese

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

composeApp/src/androidMain/kotlin/com/example/casera/network/ApiClient.android.kt

@@ -2,13 +2,19 @@ package com.example.casera.network
 
 import io.ktor.client.*
 import io.ktor.client.engine.okhttp.*
+import io.ktor.client.plugins.*
 import io.ktor.client.plugins.contentnegotiation.*
 import io.ktor.client.plugins.logging.*
 import io.ktor.serialization.kotlinx.json.*
 import kotlinx.serialization.json.Json
+import java.util.Locale
 
 actual fun getLocalhostAddress(): String = "10.0.2.2"
 
+actual fun getDeviceLanguage(): String {
+    return Locale.getDefault().language
+}
+
 actual fun createHttpClient(): HttpClient {
     return HttpClient(OkHttp) {
         install(ContentNegotiation) {
@@ -23,5 +29,9 @@ actual fun createHttpClient(): HttpClient {
             logger = Logger.DEFAULT
             level = LogLevel.ALL
         }
+
+        install(DefaultRequest) {
+            headers.append("Accept-Language", getDeviceLanguage())
+        }
     }
 }