fix: prevent permanent Android startup crash from ObjectBox corruption and malformed server URL

[richardtru]

Summary

This fixes a recurring crash pattern that has affected multiple users over several years: BlueBubbles works correctly for a few days then permanently fails to start (every launch crashes until app data is cleared). Investigation of GitHub issues (#2845 and related) revealed two independent crash paths:

Root Cause 1 — ObjectBox database corruption (primary)

After a phone OOM kill or power-off during a write transaction, the ObjectBox store files in <app_docs>/objectbox/ become corrupted. On the next launch, openStore() throws an exception. Previously there was no recovery path — the late final Store store field was never assigned, causing LateInitializationError on every subsequent access, permanently bricking the app.

Fix: Added one-shot corruption recovery to both _initDatabaseMobile and _initDatabaseDesktop: on any store open failure that isn't a concurrent-access race, the corrupted directory is renamed to a timestamped backup (objectbox_corrupted_<ms>) and a fresh store is created. Up to 2 backups are retained for diagnostics; older ones are pruned automatically.

Also moved StartupTasks.initStartupServices() inside the try/catch in main.dart so that if recovery exhausts all options, the user sees the FailureToStart widget instead of a silent blank screen.

After recovery, Database.wasRecovered is set to true and onStartup() emits a database-recovered event so the UI can surface a "Syncing messages…" notice explaining the empty chat list.

Root Cause 2 — Malformed server URL crashes the foreground service (issue #2845)

If the stored server URL contains bare % characters (e.g. %s%), socket.io's Java URLDecoder throws IllegalArgumentException in a background thread outside any try/catch in the foreground service, crashing the process. Since the foreground service starts on every launch when keepAppAlive is enabled, the app permanently crashes on every startup.

Fix: Validate the URL with java.net.URI() (synchronous, no I/O) before handing it to IO.socket(). A URISyntaxException updates the notification to "missing server URL" and returns gracefully.

Security improvements (found during review)

• Server URL no longer logged to logcat (contained auth credentials in query params)
• Custom header values no longer logged — only header keys are logged
• Socket.IO connect-error log no longer includes the server URL

Test plan

• Normal startup: Clear app data, configure server, confirm app works and "Recovery successful" does NOT appear in logs
• Simulate corruption (Android): adb shell am force-stop com.bluebubbles.messaging, then truncate <app_docs>/objectbox/data.mdb, relaunch → app recovers with empty chat list and begins syncing; objectbox_corrupted_* backup dir is present
• Malformed URL (issue Cannot Open Android App #2845): Manually set flutter.serverAddress to http://192.168.1.1:1234/%s%test in SharedPreferences, launch → foreground service logs "Server URL stored in preferences is malformed", notification updates, no crash
• Recovery failure path: Corrupt DB and set app directory to read-only → FailureToStart widget shown (not silent blank screen)
• Backup pruning: Repeat corruption 3+ times → confirm at most 2 objectbox_corrupted_* directories exist