feat: deduplicate bounties on (bounty_type, attacker_ip, payload)

Before inserting a bounty, check whether an identical row already exists.
Drops silent duplicates to prevent DB saturation from aggressive scanners.

tests/test_bounty_dedup.py

@@ -0,0 +1,84 @@
+"""
+Tests for bounty deduplication.
+
+Identical (bounty_type, attacker_ip, payload) tuples must be dropped so
+aggressive scanners cannot saturate the bounty table.
+"""
+import pytest
+from decnet.web.db.factory import get_repository
+
+
+@pytest.fixture
+async def repo(tmp_path):
+    r = get_repository(db_path=str(tmp_path / "test.db"))
+    await r.initialize()
+    return r
+
+
+_BASE = {
+    "decky": "decky-01",
+    "service": "ssh",
+    "attacker_ip": "10.0.0.1",
+    "bounty_type": "credential",
+    "payload": {"username": "admin", "password": "password"},
+}
+
+
+@pytest.mark.anyio
+async def test_duplicate_dropped(repo):
+    await repo.add_bounty({**_BASE})
+    await repo.add_bounty({**_BASE})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 1
+
+
+@pytest.mark.anyio
+async def test_different_ip_not_deduped(repo):
+    await repo.add_bounty({**_BASE})
+    await repo.add_bounty({**_BASE, "attacker_ip": "10.0.0.2"})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 2
+
+
+@pytest.mark.anyio
+async def test_different_type_not_deduped(repo):
+    await repo.add_bounty({**_BASE})
+    await repo.add_bounty({**_BASE, "bounty_type": "fingerprint"})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 2
+
+
+@pytest.mark.anyio
+async def test_different_payload_not_deduped(repo):
+    await repo.add_bounty({**_BASE})
+    await repo.add_bounty({**_BASE, "payload": {"username": "root", "password": "toor"}})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 2
+
+
+@pytest.mark.anyio
+async def test_flood_protection(repo):
+    for _ in range(50):
+        await repo.add_bounty({**_BASE})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 1
+
+
+@pytest.mark.anyio
+async def test_dict_payload_dedup(repo):
+    """Payload passed as dict (pre-serialisation path) is still deduped."""
+    await repo.add_bounty({**_BASE, "payload": {"username": "admin", "password": "password"}})
+    await repo.add_bounty({**_BASE, "payload": {"username": "admin", "password": "password"}})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 1
+
+
+@pytest.mark.anyio
+async def test_string_payload_dedup(repo):
+    """Payload passed as pre-serialised string is also deduped."""
+    import json
+    p = json.dumps({"username": "admin", "password": "password"})
+    await repo.add_bounty({**_BASE, "payload": p})
+    await repo.add_bounty({**_BASE, "payload": p})
+    bounties = await repo.get_bounties()
+    assert len(bounties) == 1