feat: forward notification images and add portable n8n workflows

[andre487]

Changes

Forward notification images alongside message text: BigPicture, MessagingStyle attachments, and optional avatars and app icons. Add JPEG/PNG selection, JPEG quality, configurable output limits, and a dedicated graphics settings section. Collection checksums participate in deduplication independently of image order.

Store images in private files outside SQLite and backups, stream encoding and upload, and bound image extraction with deadlines and a separate queue. Preserve attachments across retries and remove them after acceptance or deletion; handle missing or corrupt files without endless retries.

Keep the main-screen connection test text-only. Add a Connection test section with independent BigPicture, gallery, avatar, and app-icon options.

Provide Russian/English documentation and five importable n8n workflow levels: text webhook, image webhook, Telegram text, Telegram images with standard nodes, and advanced Telegram rich messages using N8nTelegramNode487. Include synthetic payloads, an optional dry-run cleanup workflow, and generated exports checked in CI. Examples contain no personal installation data or credentials.

Validation

• 119 Android unit tests; Android lint and debug build passed.
• 7 instrumentation tests each on API 26 and API 35 passed, including file-backed delivery, EXIF orientation, stalled image reads, and private-file isolation.
• 17 JavaScript tests and Python formatting/generation checks passed.
• All five workflow levels imported and executed on n8n 2.38.1 against a local mock Telegram API; verified duplicate suppression and resume after partial delivery failure.
• Development webhook smoke tests passed.
• Final release APK and debug instrumentation APK builds passed.

Notes

Webhook schema version remains 1 with additive image fields. Image files use Android private storage and system protection without additional application encryption. Telegram presentation depends on the client; the standard-node example uses separate media messages, while the advanced example attaches media to the first text part. Advanced delivery progress requires a configured n8n Data Table and does not guarantee exactly-once delivery across concurrent executions or crashes.

APK artifacts

• Download debug APK — signed with the disposable Android debug key
• Download unsigned release APK — verified unsigned

Built from commit 2a4866a6 by CI run #73.
Artifacts expire after 14 days. Neither APK uses the Message487 release key.