Add src/server/auth.rs with bearer_auth_middleware axum layer that
extracts the Authorization: Bearer header, resolves via
IdentityProvider::resolve_from_token, and stashes Option<Identity> in
request extensions. Shared by HTTP gateway routes and the to_mcp rmcp
service (research §4.4). No token, malformed header, or failed
resolution all yield None (unauthenticated, not an error) — Bearer-only
auth mechanism (ADR-004).
Includes ResolvedIdentity axum extractor reading from extensions, and
wires the middleware into the HttpAdapter router around the
gateway/openapi/mcp routes (excluding the raw /healthz route).
GET /healthz: raw route, no auth, no OperationContext, returns 200 OK
with plain-text 'ok' (ADR-036). Decoy fallback for unknown paths via
DecoyConfig: fake nginx 404 (default), static site serving, or redirect.
Decoy does not leak alknet presence (no alknet headers/format). Custom
routes take precedence over decoy (decoy is fallback only). Wire real
handlers into HttpAdapter router replacing placeholder 501s.
Wires the axum Router (gateway endpoints + /healthz + /openapi.json + MCP +
custom routes via extra_routes merge ADR-046) and drives hyper's HTTP/1.1 or
HTTP/2 connection driver over a single QUIC bidirectional stream. The
QUIC-to-hyper bridge wraps the (SendStream, RecvStream) pair as a
TokioIo-compatible duplex and feeds it to hyper-util's auto Builder (which
auto-detects HTTP/1.1 vs HTTP/2). h3 ALPN is not registered (ADR-044).
Route handlers, healthz/decoy logic, openapi.json, the MCP route, and the WS
upgrade handler are wired as 501 Not Implemented placeholders for their
respective tasks. The router state holds Arc<OperationRegistry> +
Arc<dyn IdentityProvider>; the router is built once at construction and
cloned per connection (cheap Arc clone). DecoyConfig defaults to NotFound.
Adds hyper-util dependency (server, service, tokio features).
