Add DM support, friend identification, and target pruning

React in 1:1 DMs alongside servers/groups, surface the resolved friend
username at startup and in the stats panel, verify reactions actually
stick after adding them (with jump links for manual spot-checking),
and prune stale targets from stats on each run so only the currently
mutual set is shown.

bot/config.py

@@ -13,6 +13,7 @@ class Config:
     db_path: str
     log_level: str
     manual_guild_ids: List[int] = field(default_factory=list)
+    verify_reactions: bool = True
 
 
 def load_config(path: str = "config.json") -> Config:
@@ -37,4 +38,5 @@ def load_config(path: str = "config.json") -> Config:
         db_path=data.get("db_path", "reactions.sqlite3"),
         log_level=data.get("log_level", "INFO"),
         manual_guild_ids=[int(g) for g in data.get("manual_guild_ids", [])],
+        verify_reactions=bool(data.get("verify_reactions", True)),
     )