Increase database connection pool limits for large printer farms

  QueuePool exhaustion at 100+ printers. Bumped pool_size 10→20,
  max_overflow 20→200, and SQLite busy_timeout 5s→15s.

CHANGELOG.md

@@ -11,6 +11,7 @@ All notable changes to Bambuddy will be documented in this file.
 - **External Folder Mounting for File Manager** ([#124](https://github.com/maziggy/bambuddy/issues/124)) — Host directories (NAS shares, USB drives, network storage) can now be mounted into the File Manager without copying files. Click "Link External" to point at a Docker bind-mounted path. Files are indexed into the database on scan but accessed directly from their original location — nothing is copied. Supports read-only mode (default, blocks uploads/moves/deletes), hidden file filtering, and automatic thumbnail extraction for 3MF, STL, gcode, and image files. External folders show a distinct icon and info bar with a rescan button. Deleting an external folder only removes the database index, never the actual files. Requested by @S1N4X.
 
 ### Fixed
+- **Database Connection Pool Exhaustion on Large Printer Farms** — Users with 100+ printers connected simultaneously experienced `QueuePool limit of size 10 overflow 20 reached, connection timed out` errors. Increased the SQLAlchemy connection pool from 30 total (10 base + 20 overflow) to 220 (20 base + 200 overflow), and raised the SQLite busy_timeout from 5 to 15 seconds to reduce write contention under heavy concurrent MQTT updates.
 - **SpoolBuddy Update Check Always Shows "Up to Date"** — The SpoolBuddy daemon update check compared the device's firmware version against GitHub releases instead of the running Bambuddy backend version. This meant the check could incorrectly report "up to date" even when the daemon was behind. Fixed by comparing directly against `APP_VERSION` from the backend config.
 - **SpoolBuddy Updates Now Use SSH** — Replaced the fragile self-update mechanism (daemon pulls its own code via git, permission errors on `.git/`, hardcoded `main` branch) with SSH-based updates driven by the Bambuddy backend. Bambuddy now SSHes into the SpoolBuddy Pi and runs git fetch/checkout, pip install, systemctl restart, and kiosk browser restart remotely. Updates automatically use the same branch as Bambuddy. SSH key pairing is fully automatic — Bambuddy generates an ED25519 keypair and includes the public key in the device registration response; the daemon deploys it to `authorized_keys` on first connect. The install script creates the `spoolbuddy` user with a bash shell and sudoers entries for daemon and kiosk restart. A "Force Update" button allows re-deploying even when versions match. The SSH public key is also shown in SpoolBuddy Settings → Updates → SSH Setup for manual pairing if needed.
 - **Frontend Not Updating After Deploy** — The service worker used stale-while-revalidate for JS/CSS assets, serving the old cached bundle even after a new build was deployed. Changed to network-first for JS/CSS (Vite content-hashes filenames so cache-busting is built in), bumped SW cache version, and added `Cache-Control: no-cache` to the `sw.js` endpoint so browsers always pick up new service worker versions immediately. The SpoolBuddy kiosk now skips SW registration entirely and unregisters any existing SW — a touchscreen kiosk has no use for offline caching and it was the main source of stale frontend issues after updates.

backend/app/core/database.py

@@ -12,7 +12,7 @@ def _set_sqlite_pragmas(dbapi_conn, connection_record):
     # WAL mode allows concurrent readers + one writer (vs default DELETE mode which locks entirely)
     cursor.execute("PRAGMA journal_mode = WAL")
     # Wait up to 5 seconds when the database is locked instead of failing immediately
-    cursor.execute("PRAGMA busy_timeout = 5000")
+    cursor.execute("PRAGMA busy_timeout = 15000")
     cursor.execute("PRAGMA synchronous = NORMAL")
     cursor.close()
 
@@ -20,8 +20,8 @@ def _set_sqlite_pragmas(dbapi_conn, connection_record):
 engine = create_async_engine(
     settings.database_url,
     echo=settings.debug,
-    pool_size=10,
-    max_overflow=20,
+    pool_size=20,
+    max_overflow=200,
 )
 
 # Register the pragma listener on the underlying sync engine
@@ -46,8 +46,8 @@ async def reinitialize_database():
     engine = create_async_engine(
         settings.database_url,
         echo=settings.debug,
-        pool_size=10,
-        max_overflow=20,
+        pool_size=20,
+        max_overflow=200,
     )
     event.listen(engine.sync_engine, "connect", _set_sqlite_pragmas)
     async_session = async_sessionmaker(