refactor: use Flask Blueprints to organize extensions

- extensions are now blueprints: keep views, templastes and statics in the same folder
- increase app security using `flask-talisman`
- whenever possible use {{ url_for }} for links between pages
- remove references to non-existing JavaScript code
- add missing favicon.ico

lnbits/wallets/lnd.py

@@ -16,7 +16,7 @@ class LndWallet(Wallet):
         r = post(
             url=f"{self.endpoint}/v1/invoices",
             headers=self.auth_admin,
-            json={"value": "100", "memo": memo, "private": True},  # , "private": True},
+            json={"value": "100", "memo": memo, "private": True},
         )
 
         if r.ok: