Persist exchange rates, selected currencies, and price source via SQLDelight

Adds a SQLDelight-backed AppDatabase (Android, Desktop, iOS/macOS) so the
converter survives restarts: the last-known rates per price source, the
user's selected fiat currencies (with order preserved), and the last-used
price source all reload before the first network fetch completes. Web isn't
a shipped platform and SQLDelight's driver there needs a worker plus a wasm
sqlite binary, so it gets a lighter localStorage-backed implementation of
the same store interfaces instead.

Android needs an app Context for its driver, wired via a new
SatsPriceApplication. iOS/macOS need libsqlite3 linked explicitly (Swift's
autolinking only covers Shared.framework itself, not its C library
dependencies), plus two extension-loading symbols marked optional since
macOS's system sqlite build omits them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QpjMKWGoiT5aJBzhxvXkwp

shared/build.gradle.kts

@@ -8,6 +8,7 @@ plugins {
     alias(libs.plugins.composeCompiler)
     alias(libs.plugins.kotlinSerialization)
     alias(libs.plugins.mokoResources)
+    alias(libs.plugins.sqldelight)
 }
 
 kotlin {
@@ -64,6 +65,7 @@ kotlin {
             implementation(libs.compose.uiToolingPreview)
             implementation(libs.compose.uiTooling)
             implementation(libs.ktor.client.okhttp)
+            implementation(libs.sqldelight.androidDriver)
         }
         commonMain.dependencies {
             implementation(libs.compose.runtime)
@@ -82,6 +84,7 @@ kotlin {
             implementation(libs.ktor.client.contentNegotiation)
             implementation(libs.ktor.serialization.kotlinxJson)
             implementation(libs.bignum)
+            implementation(libs.sqldelight.runtime)
         }
         commonTest.dependencies {
             implementation(libs.kotlin.test)
@@ -90,9 +93,14 @@ kotlin {
         }
         appleMain.dependencies {
             implementation(libs.ktor.client.darwin)
+            implementation(libs.sqldelight.nativeDriver)
         }
         jvmMain.dependencies {
             implementation(libs.ktor.client.cio)
+            implementation(libs.sqldelight.sqliteDriver)
+        }
+        webMain.dependencies {
+            implementation(libs.kotlinx.browser)
         }
         jsMain.dependencies {
             implementation(libs.wrappers.browser)
@@ -110,4 +118,12 @@ dependencies {
 
 multiplatformResources {
     resourcesPackage.set("xyz.tyiu.satsprice.shared")
-}
+}
+
+sqldelight {
+    databases {
+        register("AppDatabase") {
+            packageName.set("xyz.tyiu.satsprice.db")
+        }
+    }
+}