docker: Proxmox deployment for bot/librarian/musician + code fixes

Containerises the three services (each intended for its own Proxmox VM)
and adds the code changes needed to run cleanly on Linux/Docker.

Code fixes:
- constants.py: CONJURER_DATA_DIR roots all writable bot state under one
  mounted volume (per-variable overrides still win; native Pi unaffected)
- conjurer_librarian/search_bot.py + scrape_bot.py: the hardcoded Windows
  DOI database path (C:\Database\chunks\) is now CONJURER_LIBRARIAN_DB_PATH,
  with CONJURER_LIBRARIAN_MAXTHREADS / _CHUNK also env-overridable

Docker:
- docker/Dockerfile.{bot,librarian,musician} + compose.{bot,librarian,musician}.yaml
- docker/env/*.env.example (force-added; real *.env stays gitignored)
- docker/entrypoint.bot.sh seeds default JSON state into /data only when
  absent, so preserved history is never overwritten
- .dockerignore
- docs/deployment/DOCKER_PROXMOX.md: step-by-step runbook incl. preserving
  the existing command/conversation history and cross-VM auth

The bot image uses the vendored yt_dlp/spotify_dl forks (they win on
sys.path over the pip packages), dropping the old sed patching.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

constants.py

@@ -158,6 +158,23 @@ else:
 # Values stay as plain strings so existing ``PATH + filename`` concatenation in
 # the command modules keeps working unchanged.
 
+# Container-friendly shortcut: point CONJURER_DATA_DIR at a single mounted
+# volume and every writable data file/dir is rooted under it. The per-variable
+# CONJURER_* overrides below still take precedence, so granular control remains
+# possible and the native (Pi) deployment is unaffected when it is unset.
+_DATA_DIR = os.getenv("CONJURER_DATA_DIR")
+if _DATA_DIR:
+    LOGFILE = os.path.join(_DATA_DIR, "discord.log")
+    SETTINGS_FILE = os.path.join(_DATA_DIR, "settings.json")
+    MEMORY_FIVE_SIARA = os.path.join(_DATA_DIR, "pamiec.json")
+    MEMORY_FIVE_MUZYKA = os.path.join(_DATA_DIR, "pamiec_muzyki.json")
+    SYSTEM_GPT_SETTINGS = os.path.join(_DATA_DIR, "system_gpt_settings.json")
+    ACCIDENT_LOG = os.path.join(_DATA_DIR, "accident_log.json")
+    LOGSTORE = os.path.join(_DATA_DIR, "logs") + os.sep
+    GRAPHICS_PATH = os.path.join(_DATA_DIR, "Conjurer_graphics") + os.sep
+    MUSIC_FOLDER = os.path.join(_DATA_DIR, "music") + os.sep
+    DIR_PATH_SADOX = os.path.join(_DATA_DIR, "Fansadox") + os.sep
+
 LOGFILE = os.getenv("CONJURER_LOG_FILE", LOGFILE)
 NETRC_FILE = os.getenv("CONJURER_NETRC_FILE", NETRC_FILE)
 SETTINGS_FILE = os.getenv("CONJURER_SETTINGS_FILE", SETTINGS_FILE)