Add a single source of truth (root app.properties) for public app-wide
constants, injected at build time on both platforms instead of hardcoding.
- Apple: generate-appconfig.sh -> Generated/AppConfig.swift (wired into
`make apple-app-config`), consumed as AppConfig.privacyPolicyURL.
- KMP: generateAppConfig task -> AppConfig.kt (mirrors DiagnosticsBuildConfig),
consumed as AppConfig.PRIVACY_POLICY_URL.
Replaces the stale hardcoded privacy-policy URL on both sides with
https://vnidrop.sudosy.fr/privacy/.
Also fix the Apple release core build: disable release LTO in build-core.sh
(Cargo forbids lto in a build-override) to avoid the proc-macro
"mis-aligned LINKEDIT string pool" corruption, so release archives are
compact instead of shipping the debug core.
Update the app icon.
Tests: shell test for the generator (escaping, missing/duplicate key),
plus XCTest and jvmTest asserting the generated value matches app.properties.
Replace the legacy AppIcon.appiconset with an Icon Composer AppIcon.icon
bundle in the target's resources. ASSETCATALOG_COMPILER_APPICON_NAME already
points at "AppIcon"; the .icon back-deploys to the iOS 18.2 target.
