Add Docker deployment and per-player secret-link viewers.

Each player gets an isolated SQLite viewer via a unique URL without login, with landing page warnings to save the link and compose-based hosting for sharing with others.

Co-authored-by: Cursor <cursoragent@cursor.com>

viewers.py

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+"""Per-viewer isolation via secret URL tokens (no login)."""
+
+from __future__ import annotations
+
+import re
+import secrets
+from pathlib import Path
+
+from db import get_connection, init_db
+
+VIEWER_ID_RE = re.compile(r"^[A-Za-z0-9_-]{16,64}$")
+LOCAL_VIEWER_ID = "local"
+
+
+def generate_viewer_id() -> str:
+    return secrets.token_urlsafe(16)
+
+
+def is_valid_viewer_id(viewer_id: str) -> bool:
+    if viewer_id == LOCAL_VIEWER_ID:
+        return True
+    return bool(viewer_id and VIEWER_ID_RE.match(viewer_id))
+
+
+def viewers_dir(data_dir: Path) -> Path:
+    return data_dir / "viewers"
+
+
+def viewer_db_path(viewer_id: str, data_dir: Path) -> Path:
+    return viewers_dir(data_dir) / f"{viewer_id}.db"
+
+
+def viewer_exists(viewer_id: str, data_dir: Path) -> bool:
+    return viewer_db_path(viewer_id, data_dir).exists()
+
+
+def create_viewer(data_dir: Path) -> str:
+    """Create a new viewer with an empty SQLite database."""
+    data_dir.mkdir(parents=True, exist_ok=True)
+    viewers_dir(data_dir).mkdir(parents=True, exist_ok=True)
+
+    for _ in range(10):
+        viewer_id = generate_viewer_id()
+        db_path = viewer_db_path(viewer_id, data_dir)
+        if db_path.exists():
+            continue
+        conn = get_connection(db_path)
+        init_db(conn)
+        conn.close()
+        return viewer_id
+
+    raise RuntimeError("Could not allocate a unique viewer id")
+
+
+def ensure_local_viewer(data_dir: Path) -> str:
+    """CLI default viewer – not secret, for local single-user use."""
+    db_path = viewer_db_path(LOCAL_VIEWER_ID, data_dir)
+    if db_path.exists():
+        return LOCAL_VIEWER_ID
+    conn = get_connection(db_path)
+    init_db(conn)
+    conn.close()
+    return LOCAL_VIEWER_ID