fix(discord-bridge): director de lucru dedicat + log nedublat

- DEFAULT_CWD trece de la /workspace la /workspace/claude-agent, un spatiu cu git
  propriu, ca fisierele facute din Discord sa aiba istoric separat de proiectele
  reale. `!cd <cale>` ramane disponibil oriunde in /workspace, deci decizia din
  plan (fara allowlist de proiecte) nu se schimba.
- setup_logging: sub systemd unitul redirecteaza deja stdout in bot.log
  (StandardOutput=append:), iar FileHandler-ul scria fiecare linie a doua oara
  in acelasi fisier. FileHandler ramane doar la rulare manuala.

Verificat in productie: bot conectat, un tur real incheiat curat (inflight null,
cost $0.0742 contabilizat), restart fara orfani. Suita: 275 passed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B29CApsP1JkSdjYaGaHpE7

proxmox/lxc171-claude-agent/discord-bridge/config.py

@@ -30,7 +30,7 @@ DEFAULTS: dict[str, str] = {
     "IDLE_REAP_S": "1200",
     "RATE_PER_USER_PER_MIN": "10",
     "CLAUDE_BIN": "claude",
-    "DEFAULT_CWD": "/workspace",
+    "DEFAULT_CWD": "/workspace/claude-agent",
 }