Rename AA_ env var prefix to AGENTWRIT_

[devonartis]

Summary

Broker still uses AA_ prefix for all environment variables (AA_ADMIN_SECRET, AA_PORT, AA_BIND_ADDRESS, etc.). After the rebrand to AgentWrit, these should be AGENTWRIT_ADMIN_SECRET, AGENTWRIT_PORT, etc.

Users seeing AA_ in docker-compose or docs have no idea what it stands for without knowing the pre-rebrand history.

Affected env vars

• AA_ADMIN_SECRET → AGENTWRIT_ADMIN_SECRET
• AA_PORT → AGENTWRIT_PORT
• AA_BIND_ADDRESS → AGENTWRIT_BIND_ADDRESS
• AA_SEED_TOKENS → AGENTWRIT_SEED_TOKENS
• AA_LOG_LEVEL → AGENTWRIT_LOG_LEVEL
• AA_DB_PATH → AGENTWRIT_DB_PATH
• AA_SIGNING_KEY_PATH → AGENTWRIT_SIGNING_KEY_PATH
• AA_CONFIG_PATH → AGENTWRIT_CONFIG_PATH
• AA_TLS_MODE → AGENTWRIT_TLS_MODE
• AA_TLS_CERT → AGENTWRIT_TLS_CERT
• AA_TLS_KEY → AGENTWRIT_TLS_KEY
• AA_TLS_CLIENT_CA → AGENTWRIT_TLS_CLIENT_CA
• AA_AUDIENCE → AGENTWRIT_AUDIENCE
• AA_APP_TOKEN_TTL → AGENTWRIT_APP_TOKEN_TTL
• AA_HOST_PORT → AGENTWRIT_HOST_PORT

Approach

Accept both prefixes during transition (check AGENTWRIT_ first, fall back to AA_), then deprecate AA_ in a future release.

Workaround

Python SDK repo maps AGENTWRIT_ → AA_ in docker-compose.yml so users never see the old prefix.