Fix ntfy notifications failing with "Illegal header value" (#466)

When sending notifications with image attachments (progress/error
events), the message body was placed in an HTTP Message header. Messages
containing newlines (e.g. "Printer: file.stl\nRemaining: 4h 52m") were
rejected by httpx since HTTP headers cannot contain newline characters.
Escape newlines to literal \n which ntfy renders as line breaks.

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to Bambuddy will be documented in this file.
 - **Queue Stuck on "Busy" for "Any Model" Jobs** ([#435](https://github.com/maziggy/bambuddy/issues/435)) — When a print was queued with "Any [Model]" (e.g., "Any P1S"), it was created with `printer_id=NULL` and `target_model="P1S"`. After the assigned printer finished, the queue widget queried only for items matching `printer_id=X`, missing the next pending model-based item (`printer_id IS NULL`). With no next item found, the "Clear Plate & Start Next" button never appeared, leaving the scheduler stuck reporting "Busy". The queue API now accepts an optional `target_model` parameter; when combined with `printer_id`, it uses OR logic to also return unassigned items whose `target_model` matches the printer's model. The frontend passes the printer's model through to this query. Additionally, the backend now resolves the printer's model server-side from the database when the frontend doesn't provide `target_model` (e.g., when the printer was added without selecting a model), ensuring the OR logic works regardless of whether the client knows the printer's model.
 - **Queue "Any Model" Jobs Stuck in "Waiting" After Plate Clear** ([#435](https://github.com/maziggy/bambuddy/issues/435)) — After the queue visibility fix above, "Any Model" jobs were correctly assigned to an idle printer but immediately crashed with `'>=' not supported between instances of 'str' and 'int'` when computing AMS filament mapping. MQTT raw data returns AMS unit and tray IDs as strings, but `_build_loaded_filaments()` compared them to integers without casting. The crash prevented the assignment from committing, so the scheduler retried every 30 seconds in an infinite loop. Cast `ams_id` and `tray_id` to `int()` to match the pattern already used for external spool IDs.
 - **SD Card Cleanup After Print Never Runs** ([#374](https://github.com/maziggy/bambuddy/issues/374)) — The post-print SD card cleanup (which deletes uploaded gcode from the printer root to prevent phantom prints on power cycle) used `printer_manager.get_printer()`, which returns a `PrinterInfo` with only `name` and `serial_number`. Accessing `.ip_address`, `.access_code`, and `.model` raised `AttributeError`, silently caught by the outer exception handler. Replaced with a DB query for the `Printer` model, matching the pattern used everywhere else in `on_print_complete()`.
+- **ntfy Notifications Fail With "Illegal header value"** ([#466](https://github.com/maziggy/bambuddy/issues/466)) — When sending ntfy notifications with image attachments (progress, error events), the message body was placed in an HTTP `Message` header. Multi-line messages (e.g., printer name + remaining time) contain newline characters, which are illegal in HTTP headers. Test notifications worked because they are single-line with no image. Now escapes newlines to literal `\n` in the header, which ntfy interprets and renders as actual line breaks.
 - **Inventory Date Format Ignores Settings** ([#463](https://github.com/maziggy/bambuddy/issues/463)) — The inventory page used a local `formatDate()` that hardcoded the `en-GB` locale, always displaying dates in a fixed format regardless of the date format setting. Now fetches the `date_format` setting and uses the shared `formatDateInput()` utility which formats as MM/DD/YYYY, DD/MM/YYYY, YYYY-MM-DD, or browser locale based on the user's choice.
 - **Inventory Location Shows Garbled Characters for AMS-HT Slots** ([#463](https://github.com/maziggy/bambuddy/issues/463)) — The inventory location column computed slot letters via `String.fromCharCode(65 + ams_id)`, which produced accented characters (e.g., `Á`) for AMS-HT units (ams_id ≥ 128). Now uses the shared `formatSlotLabel()` utility which correctly handles AMS-HT and external spool slots.
 

backend/app/services/notification_service.py

@@ -208,9 +208,11 @@ class NotificationService:
         client = await self._get_client()
 
         if image_data:
-            # ntfy supports image attachments via multipart form-data
+            # ntfy supports image attachments via multipart form-data.
+            # HTTP headers cannot contain newlines, but ntfy interprets
+            # literal \n (backslash-n) as newlines in the Message header.
             headers["Filename"] = "photo.jpg"
-            headers["Message"] = message
+            headers["Message"] = message.replace("\n", "\\n")
             response = await client.put(url, content=image_data, headers=headers)
         else:
             response = await client.post(url, content=message, headers=headers)