feat: add live replays and PostgreSQL maintenance tools

- Stream compact live replay updates across local and clustered dashboards.
- Render responsive snake bodies as SVG paths with aligned custom icons.
- Add cache-busted assets, replay fallback routes, and live-follow playback.
- Support PostgreSQL benchmark sampling and idempotent SQLite migration.
- Add dry-run cleanup for old low-quality PostgreSQL replay payloads.
- Reward safe perimeter lanes and bump Prism to version 1.5.0.
- Add backend, migration, dashboard, and perimeter regression coverage.

server/database/backend/PostgresqlGameplayBackend.py

@@ -12,7 +12,7 @@ Connection: pass a DSN via the `dsn` constructor argument, e.g.
 or set GAMEPLAY_DB_PG_DSN in the environment.
 """
 
-import asyncio, json, logging, sqlite3, sys
+import asyncio, logging, sqlite3, json, sys
 from datetime import datetime, timezone
 from pathlib import Path
 from urllib.parse import urlparse, urlunparse
@@ -263,11 +263,20 @@ class PostgresqlGameplayBackend(GameplayBackendTemplate):
     conn.row_factory = sqlite3.Row
 
     try:
-      games = conn.execute("""
+      game_columns = {
+        row["name"] for row in conn.execute("PRAGMA table_info(games)").fetchall()
+      }
+      if "winner_name" in game_columns:
+        winner_name_expression = "winner_name"
+      elif "winner_names_json" in game_columns:
+        winner_name_expression = "winner_names_json"
+      else:
+        winner_name_expression = "NULL"
+      games = conn.execute(f"""
         SELECT game_id, started_at, ended_at, width, height, source, map_name,
           ruleset_name, ruleset_version, your_snake_id, your_snake_name,
           your_snake_type, your_snake_version, game_type,
-          winner_names_json, winner_you, final_turn, status
+          {winner_name_expression} AS winner_name, winner_you, final_turn, status
         FROM games
         ORDER BY started_at ASC
       """).fetchall()
@@ -301,6 +310,15 @@ class PostgresqlGameplayBackend(GameplayBackendTemplate):
     except (json.JSONDecodeError, TypeError):
       return None
 
+  def _migrated_winner_name(self, value:str|None) -> str|None:
+    """Accept both the current winner_name and legacy winner_names_json value."""
+    if not value:
+      return None
+    parsed = self._parse_json(value)
+    if isinstance(parsed, list):
+      return next((str(name) for name in parsed if name), None)
+    return value
+
   async def _insert_migrated_data(self, games:list, turns:list, snake_turns:list) -> None:
     assert self._pool is not None
     async with self._pool.acquire() as conn:
@@ -332,7 +350,7 @@ class PostgresqlGameplayBackend(GameplayBackendTemplate):
               row["your_snake_type"],
               row["your_snake_version"],
               row["game_type"],
-              (self._parse_json(row["winner_names_json"]) or [None])[0],
+              self._migrated_winner_name(row["winner_name"]),
               bool(row["winner_you"]),
               row["final_turn"],
               row["status"],