fix: keep whole SIP messages out of WARN logs

[tgeorge06]

Fixes #177.

Problem

Some WARN records print a whole SIP message, with the From/To/Contact URIs, display names and the body:

• DialogInner::send_prack_request and send_dialog_request print the whole request when tx.send() fails (src/dialog/dialog.rs:707, tx.original at line 712; dialog.rs:1153, req = %tx.original at line 1156).
• WebSocketConnection::serve_loop prints the raw text frame when it does not parse (src/transport/websocket.rs:343).
• The "bye skipped" WARN of ClientInviteDialog, InviteDialog and ServerInviteDialog (client_dialog.rs:163, invite_dialog.rs:430, server_dialog.rs:357) logs state = ?self.state(), and the returned error formats the state with {:?}. DialogState::Early, WaitAck and Confirmed hold the whole Response (dialog.rs:117-119), and Debug prints it.

WARN usually goes to production logs, and those fields are personal data (phone numbers, user names, SDP addresses).

Fix

• Send failure: the WARN keeps its fields (id, destination, the error) and adds method; the request is logged right after it at DEBUG ("request that failed to send", with id and req).
• WebSocket parse failure: the WARN logs len instead of the frame. The frame is already logged at INFO when it is received (websocket.rs:323), so nothing new is needed at DEBUG. This is how the binary-frame branch (websocket.rs:367) and the UDP transport (udp.rs:184, at DEBUG) already behave.
• Skipped BYE: the WARN and the returned error use the existing Display of DialogState (dialog.rs:1642), which prints the dialog id and the state name (<id>(Early)) and never the embedded message.

Contract / coverage

What each WARN contains now:

• "failed to send request error: <error>": id (the dialog id: Call-ID, local and remote tag), destination (transport and host:port, when known), method. The Call-ID and tags were already in this WARN and are kept: they are the identifiers an operator needs to find the call, and they carry no URI or display name. The error is the transaction's own Display; the in-tree send errors name an address or a transaction key, never the request (a custom TargetLocator controls the text of its own error).
• "Error parsing SIP message" (WebSocket text frame): error, src, len. The parser's error can quote the start-line token it rejected (for example invalid method: NOT), as the binary-frame branch and the stream transport already log; not changed here.
• "bye skipped: ...": dialog_id, state as <id>(<State>).

Full messages are still logged where they were, below WARN: the failed request at DEBUG next to its WARN, received WebSocket text at INFO, sent and received messages in the transports at INFO.

Behaviour change: the error returned by bye_with_headers (and bye) on a dialog that is not confirmed reads dialog <id> cannot send BYE in state <id>(Early) instead of the Debug dump. No caller in the repository matches on it.

Checked and not changed: every other warn! / error! in src/. None prints a message or a type whose Debug embeds one (DialogSnapshotState and TransactionState are plain enums; SendError's Debug omits its payload).

Tests

New src/dialog/tests/test_warn_logs.rs, with a small capturing tracing::Subscriber (the crate has no tracing-subscriber dev-dependency; tracing-subscriber is only enabled by the bench feature). Each test puts a marker in the From display name and URI user part and asserts that the WARN does not contain it:

• test_failed_request_send_warns_without_the_request: a UAC dialog on an endpoint whose TargetLocator always fails. An INFO through do_request (send_dialog_request) and a PRACK through send_prack_request each give one WARN with method=INFO / method=PRACK and without the marker, and one DEBUG record with it.
• test_bye_in_early_state_warns_without_the_response: the dialog in Early with a 180 carrying the marker; bye() on ClientInviteDialog, InviteDialog and ServerInviteDialog each fails with an error that reads (Early) and has no marker, and the three WARNs have none.
• test_websocket_parse_failure_warns_without_the_message (websocket feature): a WebSocket server sends one unparsable text frame to WebSocketConnection::serve_loop. The WARN has len and no marker; the INFO record of the received frame still has it.

On main (5ef8ea6) all three fail:

---- dialog::tests::test_warn_logs::test_failed_request_send_warns_without_the_request stdout ----
panicked at src/dialog/tests/test_warn_logs.rs:118:5:
[" message=failed to send request error: Error: no route id=\"warn-call-a-b\" req=INFO sip:bob@127.0.0.1:5999 SIP/2.0\r\nVia: SIP/2.0/UDP 127.0.0.1;branch=z9hG4bKwarn\r\nCSeq: 2 INFO\r\nFrom: \"private-marker\" <sip:private-marker@example.com>;tag=a\r\n...

---- dialog::tests::test_warn_logs::test_bye_in_early_state_warns_without_the_response stdout ----
panicked at src/dialog/tests/test_warn_logs.rs:151:9:
Error: dialog warn-call-a-b cannot send BYE in state Early(DialogId { call_id: "warn-call", local_tag: "a", remote_tag: "b" }, Response { status_code: Ringing, version: V2, headers: Headers([... From(From("\"private-marker\" <sip:private-marker@example.com>;tag=a")), ...]), body: [] })

---- dialog::tests::test_warn_logs::test_websocket_parse_failure_warns_without_the_message stdout ----
panicked at src/dialog/tests/test_warn_logs.rs:190:5:
[" message=Error parsing SIP message error=rsip error: could not parse part: invalid method: NOT src=WS 127.0.0.1:49711 raw_message=\"NOT SIP <sip:private-marker@example.com>\\r\\n\\r\\n\""]

Checks

• cargo test --features bench: 388 lib tests passed, 0 failed (385 on main plus the three new ones), and 65 doc tests passed. Plain cargo test passes too.
• cargo check --no-default-features --features platform-embassy: no warnings, as on main.
• cargo clippy --features bench --all-targets: the same output as on main, none in the changed code. (On main it stops at a clippy::never_loop error in src/dialog/tests/test_refer_notify.rs:98, unrelated to this PR.)
• rustfmt --check on the changed files: clean.
• Merges cleanly with fix: keep confirmed dialogs confirmed on 1xx to in-dialog requests #147, fix: notify dialog state only for transitions that are applied #148, fix(transaction): keep a server INVITE's final response after the ACK ends it #174 and fix(dialog): get_client_dialog_by_call_id returns only UAC dialogs #176; with all five merged all tests pass (396 lib tests).