d371c1d931
MemoryClient and AsyncMemoryClient hardcoded the default host, so a self-hosted or proxied deployment had to pass host= at every construction site even with MEM0_HOST exported. The API key already reads from the environment; the host now does too. Resolution order: explicit host argument, MEM0_HOST, MEM0_API_URL, then https://api.mem0.ai. Existing callers are unaffected. Closes #6622