Align OTR plugin integration with XEP-0364

[Ri0n]

Summary

This keeps the native qca-otr protocol implementation unchanged and updates only the Psi-side OTR adapter/integration.

• keep the exact XMPP endpoint JID supplied by routing: native XMPP resources stay full JIDs, while bare JIDs from XMPP transports remain valid OTR endpoints
• use XEP-0378 caps (urn:xmpp:otr:0) and incoming OTR EME as strong endpoint-scoped signals for XEP-0364 payload semantics
• preserve legacy OTR HTML semantics for endpoints without those XEP signals: authenticated decrypted rich text is normalized with HtmlNormalizer, while XEP-0364 peers always treat decrypted XML-looking content as literal text
• use raw plaintext for XEP-0364 peers and legacy HTML escaping for legacy peers before OTR encryption
• feed whitespace-tagged plaintext through qca-otr so Opportunistic/Always policies can react to the discovery tag, while keeping the original plaintext message visible
• recognize exact OTRv1/v2/v3 whitespace version tags and record v3 capability per exact endpoint
• add XEP-0364 processing hints consistently; emit OTR EME only for endpoints known to use XEP-0364 semantics
• silently ignore OTR protocol traffic received through Message Carbons
• expire discovery/payload-mode state per exact endpoint on unavailable presence and per account on logout
• remove obsolete online/login bookkeeping and the old full-to-bare JID normalization helper

The legacy chat menu remains for SMP, session ID, fingerprint and explicit session control. Bare transport endpoints are allowed there as well.

qca-otr is intentionally unchanged.