Filter non-actionable HMS errors from notifications (#470)

Infrastructure/auth HMS error codes like 0500_0007 (MQTT command
verification failed) triggered false-alarm printer error notifications
even though they don't indicate actual print problems.

- Add suppress list for non-actionable error codes: 0500_0007 (MQTT
  auth failure), 0500_4001 (cloud connection failure), 0500_400E
  (print cancelled by user)
- Skip suppressed codes in the notification loop so they are still
  tracked in HMS state and shown in the UI, but don't fire notifications

CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to Bambuddy will be documented in this file.
 ## [0.2.1b2] - Unreleased
 
 ### Fixed
+- **Non-Actionable HMS Errors Triggering Notifications** ([#470](https://github.com/maziggy/bambuddy/issues/470)) — Infrastructure and auth-related HMS error codes (like `0500_0007` "MQTT command verification failed") were triggering printer error notifications even though they don't indicate actual print problems. For example, a device with incorrect bind settings sending unauthorized MQTT commands caused repeated false-alarm nozzle/extruder error notifications with camera snapshots of perfectly fine prints. Now suppresses notifications for known non-actionable error codes: `0500_0007` (MQTT auth failure), `0500_4001` (Bambu Cloud connection failure), and `0500_400E` (print cancelled by user).
 - **Support Bundle Leaking Personal Data** ([#473](https://github.com/maziggy/bambuddy/issues/473)) — The support bundle's log sanitizer only used regex patterns, which can't detect arbitrary user-chosen strings like printer names and usernames. Now queries the database for known sensitive values (printer names, serial numbers, auth usernames, Bambu Cloud email) and does exact-string replacement before the regex pass. Serial number regex no longer leaks the first 3 characters (was using a capture group for partial redaction). Tasmota smart plug credentials embedded in URLs (`http://user:pass@host`) were logged verbatim by httpx; now uses httpx's `auth` parameter for HTTP Basic auth so credentials never appear in the URL. Added `username` and `path` to the settings key filter to redact `smtp_username` and `slicer_binary_path` from the support info JSON. A URL credentials regex provides defense-in-depth for any remaining `user:pass@` patterns in logs. IP addresses are no longer redacted from the bundle as they are needed for connectivity debugging. Updated the frontend privacy disclaimer and wiki documentation to reflect the new behavior.
 - **Spool Usage Lost When Spool Runs Empty Mid-Print** ([#459](https://github.com/maziggy/bambuddy/issues/459)) — When a spool ran empty during a print and the AMS auto-switched to a backup spool, the `on_ams_change` handler eagerly deleted the empty spool's `SpoolAssignment` record (fingerprint mismatch). When `on_print_complete` later ran, it queried `SpoolAssignment` live from the database, found nothing, and silently dropped usage. Now snapshots all spool assignments at print start into the `PrintSession`, so usage is correctly attributed at completion regardless of mid-print AMS changes.
 - **K-Profile Response Race Condition Crash** ([#462](https://github.com/maziggy/bambuddy/issues/462)) — An unsolicited or late K-profile MQTT response could crash the MQTT handler with `AttributeError: 'NoneType' object has no attribute 'set'`. The MQTT callback thread checked `self._pending_kprofile_response` (not None) at line 2698, but between that check and the `.set()` call, the asyncio thread's `finally` block in `get_kprofiles()` could clear the attribute to `None` after a timeout — a classic TOCTOU race. Fixed by capturing the event reference in a local variable before the check.

backend/app/main.py

@@ -431,6 +431,14 @@ async def on_printer_status_change(printer_id: int, state: PrinterState):
         # Reset milestone tracking when print restarts or new print begins
         _last_progress_milestone[printer_id] = 0
 
+    # HMS error codes that should not trigger notifications.
+    # These are infrastructure/auth issues, not actionable print errors.
+    _HMS_NOTIFICATION_SUPPRESS = {
+        "0500_0007",  # MQTT command verification failed (auth/bind issue, not a print error)
+        "0500_4001",  # Failed to connect to Bambu Cloud (network issue)
+        "0500_400E",  # Printing was cancelled (user action, not an error)
+    }
+
     # Check for new HMS errors and send notifications
     current_hms_errors = getattr(state, "hms_errors", []) or []
     if current_hms_errors:
@@ -483,6 +491,9 @@ async def on_printer_status_change(printer_id: int, state: PrinterState):
                         error_code_masked = error_code_int & 0xFFFF
                         short_code = f"{(error.attr >> 16) & 0xFFFF:04X}_{error_code_masked:04X}"
 
+                        if short_code in _HMS_NOTIFICATION_SUPPRESS:
+                            continue
+
                         error_type = f"{module_name} Error"
                         # Look up human-readable description
                         description = get_error_description(short_code)