Fix duplicate mod checkboxes, add i18n (ru, de)

[HugeFrog24]

1. Bug fix: Duplicate mod checkboxes in Canvas Menu

Problem

Launching the game multiple times without the process dying causes duplicate checkboxes for the same mod in the ImGui Canvas Menu:

How it happens

When the user swipes Canvas from recents, Android may keep the process alive, particularly if the LogcatMonitorService foreground service is running, or due to normal process caching. The native library and its static state survive. If the user then reopens Canvas, manages mods (delete/re-add), and launches the game again, onModLibrary pushes new entries into the userLibs vector alongside stale ones from the previous session.

The /proc/self/maps deduplication in ElfLoader is also bypassed in this scenario, because a deleted-then-re-added .so file appears as "mod.so (deleted)" in the maps, which doesn't match the new filename.

Steps to reproduce (deterministic, via adb)

1. Install a mod
2. Launch the game
3. While the game is running, bring ModManagerActivity to the front:
   adb shell am start -n git.artdeell.skymodloader/.elfmod.ModManagerActivity
4. Delete the mod
5. Re-add it
6. Launch the game again
7. Each launch adds another duplicate entry

Fix

Added Canvas::userLibs.clear() at the top of settle(), which runs once per game launch before any mods are registered. This ensures a clean slate regardless of prior process state.

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2. Feature: i18n support (Russian, German)

What changed

• Migrated ~50 hardcoded strings from layout XML and Java code to strings.xml
• Marked non-translatable strings (file paths, format strings, brand names) with translatable="false"
• Added Russian (values-ru) and German (values-de) translations (native speaker of both)
• Added locales_config.xml for per-app language switching on Android 13+
• Fixed typos: "Annulla" → "Cancel", "NATRUAL" → "NATURAL"

Testing

• Verified duplicate checkbox bug no longer reproduces
• Build passes (./gradlew assembleDebug)
• Test Russian/German translations on device with per-app language switching