docs: complete Phase 0 architecture — spec updates, review fixes, and link portability

Update four existing specs (overview, server, napi-and-pubsub, call-protocol) to
reflect Phase 0 decisions: three-layer model, IdentityProvider, ForwardingPolicy,
OperationEnv, static/dynamic config split. Review all 9 Phase 0a ADRs (026-034)
for consistency. Fix 4 critical issues from architecture review: missing OQ-SVC-05
in open-questions.md, deprecated hub terminology, undefined AuthService and noq
terms. Replace inline OQ text with cross-references per format rules. Add
ConfigServiceImpl definition to configuration.md. Port absolute workspace paths
to project-relative links by copying referenced docs (feasibility, certbot,
fail2ban, event_source_types) into docs/research/.

docs/architecture/decisions/001-pluggable-transport.md

@@ -23,4 +23,4 @@ This makes adding a new transport (e.g., WebSocket, QUIC directly) a matter of i
 
 ## References
 - [transport.md](../transport.md)
-- [Feasibility assessment §3](../../../../conversations/research/ssh-tunnel-vpn-alternative-feasibility.md)
+- [Feasibility assessment §3](../../research/feasibility/ssh-tunnel-vpn-alternative-feasibility.md)