feat: native shopping list — decouple from Bring! (#105)

- New shopping_list SQLite table (migration in migrateDB)
- shoppingGetList/Add/Remove — delegates to Bring! or internal DB
  based on SHOPPING_MODE env var (default: internal)
- isShoppingBringMode() guard: requires mode=bring + BRING credentials
- bringQuickSyncProduct updated to support both modes
- All bring_* JS calls replaced with shopping_* (bring_migrate_names kept)
- New settings tab 'Lista spesa' (tab-bring) with:
  - Enable/disable shopping list toggle
  - Provider radio: internal vs Bring!
  - Bring! sub-section (shown only when mode=bring)
  - AI smart suggestions toggle
  - Forecast toggle
  - Auto-add threshold (qty slider)
  - Price estimation section
- _applyShoppingSettingsUI, onShoppingEnabledChange, onShoppingModeChange
- SHOPPING_* env vars documented in .env.example
- cron_smart_shopping respects SHOPPING_MODE and SHOPPING_SMART_SUGGESTIONS
- Translations: 12 new keys in all 5 languages (it/en/de/fr/es)
- DB busy_timeout=5000ms + WAL pragma in getDB() (fixes #95)

.env.example

@@ -89,6 +89,41 @@ PRICE_CURRENCY=EUR
 # PRICE_UPDATE_MONTHS: how many months to cache a price before re-fetching (default 3)
 PRICE_UPDATE_MONTHS=3
 
+# ── Cleanup / retention ──────────────────────────────────────────────────────
+# RECIPE_RETENTION_DAYS: delete auto-generated recipe plans older than N days
+RECIPE_RETENTION_DAYS=7
+# TRANSACTION_RETENTION_DAYS: keep stock transaction history for N days.
+# Smart Shopping uses this history to compute purchase frequencies.
+# WARNING: values below 30 will cause the shopping list to appear nearly empty.
+# Minimum enforced at runtime: 30 days.
+TRANSACTION_RETENTION_DAYS=90
+
+# ── Local Backup ─────────────────────────────────────────────────────────────
+# BACKUP_ENABLED: run a daily incremental backup via cron (true/false)
+BACKUP_ENABLED=true
+# BACKUP_RETENTION_DAYS: keep local backups for N days (minimum 1)
+BACKUP_RETENTION_DAYS=3
+
+# ── Google Drive Backup ───────────────────────────────────────────────────────
+# GDRIVE_ENABLED: upload the daily backup to Google Drive (requires a service account)
+GDRIVE_ENABLED=false
+#
+# Setup steps:
+#   1. Create a Google Cloud project and enable the Drive API
+#   2. Create a Service Account and download the JSON key
+#   3. Create a Drive folder and share it with the service account email
+#   4. Paste the JSON content below (or set GDRIVE_SERVICE_ACCOUNT_FILE to the path)
+#   5. Set GDRIVE_FOLDER_ID to the Drive folder ID (from its URL)
+#
+# GDRIVE_SERVICE_ACCOUNT_JSON: full JSON content of the service account key
+GDRIVE_SERVICE_ACCOUNT_JSON=
+# GDRIVE_SERVICE_ACCOUNT_FILE: alternative — path to the service account JSON file
+GDRIVE_SERVICE_ACCOUNT_FILE=
+# GDRIVE_FOLDER_ID: ID of the Drive folder where backups will be stored
+GDRIVE_FOLDER_ID=
+# GDRIVE_RETENTION_DAYS: delete Drive backups older than N days (0 = keep all)
+GDRIVE_RETENTION_DAYS=30
+
 # ── Security ─────────────────────────────────────────────────────────────────
 # SETTINGS_TOKEN: if set, the Settings screen requires this token to save changes.
 # Leave empty to allow anyone with access to the server to change settings.