feat: cleanup-wallets cli command (#2176)

* feat: `cleanup-wallet` cli command
`lnbits-cli db cleanup-wallets` removes all wallets that never had an transaction.
this helps against spammers creating random wallets, eventually slowing down the db.
* add commands
* add to example env
* db_versions was used in app
* add delta as cli argument
* use days unit
* simplify cli argument name (cleanup_wallet_days -> days)!

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Co-authored-by: Vlad Stan <stan.v.vlad@gmail.com>
Co-authored-by: Pavol Rusnak <pavol@rusnak.io>

lnbits/settings.py

@@ -348,6 +348,7 @@ class EnvSettings(LNbitsSettings):
     log_retention: str = Field(default="3 months")
     server_startup_time: int = Field(default=time())
     lnbits_extensions_deactivate_all: bool = Field(default=False)
+    cleanup_wallets_days: int = Field(default=90)
 
     @property
     def has_default_extension_path(self) -> bool: