feat: attacker profiles — UUID model, API routes, list/detail frontend

Migrate Attacker model from IP-based to UUID-based primary key with
auto-migration for old schema. Add GET /attackers (paginated, search,
sort) and GET /attackers/{uuid} API routes. Rewrite Attackers.tsx as
a card grid with full threat info and create AttackerDetail.tsx as a
dedicated detail page with back navigation, stats, commands table,
and fingerprints.

decnet/web/db/models.py

@@ -53,7 +53,8 @@ class State(SQLModel, table=True):
 
 class Attacker(SQLModel, table=True):
     __tablename__ = "attackers"
-    ip: str = Field(primary_key=True)
+    uuid: str = Field(primary_key=True)
+    ip: str = Field(index=True)
     first_seen: datetime = Field(index=True)
     last_seen: datetime = Field(index=True)
     event_count: int = Field(default=0)