feat: add is_bot_message column and support dedicated phone numbers (#235)

* feat: add is_bot_message column and support dedicated phone numbers

Replace fragile content-prefix bot detection with an explicit
is_bot_message database column. The old prefix check (content NOT LIKE
'Andy:%') is kept as a backstop for pre-migration messages.

- Add is_bot_message column with automatic backfill migration
- Add ASSISTANT_HAS_OWN_NUMBER env var to skip name prefix when the
  assistant has its own WhatsApp number
- Move prefix logic into WhatsApp channel (no longer a router concern)
- Remove prefixAssistantName from Channel interface
- Load .env via dotenv so launchd-managed processes pick up config
- WhatsApp bot detection: fromMe for own number, prefix match for shared

Based on #160 and #173.

Co-Authored-By: Stefan Gasser <stefan@stefangasser.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: extract shared .env parser and remove dotenv dependency

Extract .env parsing into src/env.ts, used by both config.ts and
container-runner.ts. Reads only requested keys without loading secrets
into process.env, avoiding leaking API keys to child processes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Stefan Gasser <stefan@stefangasser.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/config.ts

@@ -1,6 +1,16 @@
 import path from 'path';
 
-export const ASSISTANT_NAME = process.env.ASSISTANT_NAME || 'Andy';
+import { readEnvFile } from './env.js';
+
+// Read config values from .env (falls back to process.env).
+// Secrets are NOT read here — they stay on disk and are loaded only
+// where needed (container-runner.ts) to avoid leaking to child processes.
+const envConfig = readEnvFile(['ASSISTANT_NAME', 'ASSISTANT_HAS_OWN_NUMBER']);
+
+export const ASSISTANT_NAME =
+  process.env.ASSISTANT_NAME || envConfig.ASSISTANT_NAME || 'Andy';
+export const ASSISTANT_HAS_OWN_NUMBER =
+  (process.env.ASSISTANT_HAS_OWN_NUMBER || envConfig.ASSISTANT_HAS_OWN_NUMBER) === 'true';
 export const POLL_INTERVAL = 2000;
 export const SCHEDULER_POLL_INTERVAL = 60000;