feat(creds): Phase 1 — Authorization header + SNMP community capture

Closes the cred-coverage gap for 7 services that already had the data
on the wire but never landed it in the Credential table:

- SNMP — community string lands as secret_kind="snmp_community",
  principal=None (v1/v2c has no per-user identity, the community IS
  the auth).
- SIP — Digest response hash, previously buried in the auth= header
  dump, now classify_authorization()-extracted.
- HTTP / HTTPS — Authorization header was in the headers JSON but
  never extracted. Now Basic decodes to plaintext, Bearer →
  http_bearer (principal=None), Digest → http_digest_md5.
- K8s — already extracted Authorization but didn't normalize. Service-
  account JWTs flow through as Bearer.
- Docker API — headers absent entirely. Adds the headers JSON dump
  and runs Authorization through the classifier.
- Elasticsearch — five distinct request handlers; each gains a
  per-handler _cred_fields() helper.

Adds canonical templates/syslog_bridge.py:classify_authorization().
Recognised: Basic / Bearer / Token / Digest. Unknown schemes (NTLM,
AWS4-HMAC, Negotiate) return None; the header still rides in the
ambient SD-block but isn't normalized as a credential. The SD shape
on the wire collapses sip_digest_md5 into http_digest_md5 — same
algorithm, so cross-protocol reuse correlates correctly when (rare)
nonce collisions allow.

Drive-by repair of tests/core/test_fingerprinting.py:

- The pre-existing `test_http_useragent_extracted` asserted both that
  add_bounty was called exactly once AND that the UA payload carried
  `path` and `method` fields. Both wrong since this session opened:
  the http_quirks fingerprint added later fires too, and the UA
  payload never actually included path/method despite the assertion.
- Adds `path`/`method` to the UA fingerprint payload (real operator
  value: "Nikto hit /admin" beats "Nikto seen on this decky").
- Replaces `assert_awaited_once` with a `_find_ua_bounty()` helper
  that filters add_bounty calls by `fingerprint_type`. New fingerprint
  families landing later won't retroactively break old tests.
- Updates the two credential-bearing tests to use the post-DEBT-039
  native shape (`secret_b64` / `principal`) and `upsert_credential`,
  not the deleted legacy `username+password` adapter.

Also rebuilds the per-service fake `syslog_bridge` modules in
tests/service_testing/{conftest,test_imap,test_pop3,test_snmp,test_mqtt,test_smtp}.py
to expose `encode_secret` + `classify_authorization`. Service templates
that import either now no longer fail at test collection.

173 tests pass in the touched scope. Phases 2-7 still pending.

tests/services/test_syslog_bridge_helpers.py

@@ -65,6 +65,53 @@ def test_encode_secret_preserves_rfc5424_specials(syslog_bridge):
     assert base64.b64decode(out["secret_b64"]) == secret.encode("utf-8")
 
 
+def test_classify_authorization_basic(syslog_bridge):
+    """HTTP Basic — base64(user:pw) decodes to plaintext credential."""
+    cred = syslog_bridge.classify_authorization("Basic YWRtaW46aHVudGVyMg==")
+    assert cred is not None
+    assert cred["principal"] == "admin"
+    assert cred["secret_kind"] == "plaintext"
+    assert base64.b64decode(cred["secret_b64"]) == b"hunter2"
+    assert cred["secret_printable"] == "hunter2"
+
+
+def test_classify_authorization_bearer(syslog_bridge):
+    cred = syslog_bridge.classify_authorization("Bearer eyJhbGciOiJIUzI1NiJ9.foo.bar")
+    assert cred["principal"] is None
+    assert cred["secret_kind"] == "http_bearer"
+    assert base64.b64decode(cred["secret_b64"]) == b"eyJhbGciOiJIUzI1NiJ9.foo.bar"
+
+
+def test_classify_authorization_token_alias(syslog_bridge):
+    """`Token <opaque>` = same shape as Bearer (Kubernetes service accounts)."""
+    cred = syslog_bridge.classify_authorization("Token sa-jwt-token-abc")
+    assert cred["secret_kind"] == "http_bearer"
+
+
+def test_classify_authorization_digest(syslog_bridge):
+    """RFC 7616 Digest — extract username + response hash."""
+    header = ('Digest username="alice", realm="example.com", '
+              'nonce="abc123", uri="/", response="d41d8cd98f00b204e9800998ecf8427e"')
+    cred = syslog_bridge.classify_authorization(header)
+    assert cred["principal"] == "alice"
+    assert cred["secret_kind"] == "http_digest_md5"
+    assert cred["secret_printable"] == "d41d8cd98f00b204e9800998ecf8427e"
+
+
+def test_classify_authorization_unknown_scheme(syslog_bridge):
+    """NTLM, AWS4-HMAC-…, Negotiate — all return None for now."""
+    assert syslog_bridge.classify_authorization("NTLM TlRMTVNTUAA=") is None
+    assert syslog_bridge.classify_authorization("AWS4-HMAC-SHA256 Credential=…") is None
+
+
+def test_classify_authorization_malformed(syslog_bridge):
+    assert syslog_bridge.classify_authorization(None) is None
+    assert syslog_bridge.classify_authorization("") is None
+    assert syslog_bridge.classify_authorization("Basic !!not-base64!!") is None
+    assert syslog_bridge.classify_authorization("Basic dXNlcg==") is None  # no colon
+    assert syslog_bridge.classify_authorization("Digest no-response-here") is None
+
+
 def test_encode_secret_unicode_replaced(syslog_bridge):
     """Non-ASCII unicode encodes via utf-8, then printable strips the
     multi-byte sequence to '?' chars (one per raw byte)."""