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/env.ts

@@ -0,0 +1,40 @@
+import fs from 'fs';
+import path from 'path';
+
+/**
+ * Parse the .env file and return values for the requested keys.
+ * Does NOT load anything into process.env — callers decide what to
+ * do with the values. This keeps secrets out of the process environment
+ * so they don't leak to child processes.
+ */
+export function readEnvFile(keys: string[]): Record<string, string> {
+  const envFile = path.join(process.cwd(), '.env');
+  let content: string;
+  try {
+    content = fs.readFileSync(envFile, 'utf-8');
+  } catch {
+    return {};
+  }
+
+  const result: Record<string, string> = {};
+  const wanted = new Set(keys);
+
+  for (const line of content.split('\n')) {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.startsWith('#')) continue;
+    const eqIdx = trimmed.indexOf('=');
+    if (eqIdx === -1) continue;
+    const key = trimmed.slice(0, eqIdx).trim();
+    if (!wanted.has(key)) continue;
+    let value = trimmed.slice(eqIdx + 1).trim();
+    if (
+      (value.startsWith('"') && value.endsWith('"')) ||
+      (value.startsWith("'") && value.endsWith("'"))
+    ) {
+      value = value.slice(1, -1);
+    }
+    if (value) result[key] = value;
+  }
+
+  return result;
+}