fix(web): disable anonymous login by default (guest button removal)

claudemesh requires an account — mesh membership is tied to user.id.
e8ad7a5 flipped the config default but the env var override at
env.config.ts:43 still defaulted to true, keeping the button visible.

Fixed at env var level + example files. Needs Coolify rebuild since
NEXT_PUBLIC_* is build-time in Next standalone.

.nano-banana-config.json

@@ -0,0 +1,3 @@
+{
+  "geminiApiKey": "AIzaSyBblLRkmypvabqI-xJ_b2KPVA9Pswtav0M"
+}