fix(channels): wire Teams inbound through the generic webhook route

[RameshHertzai]

Problem

Microsoft Teams had a working outbound path (BotFrameworkAdapter) but no inbound one — TeamsAdapter.process_activity() was never reached by any HTTP route. Teams could send but not receive: listed in the channel catalog, half-connected.

Bot Framework can't ride the existing generic webhook auth model as-is: it POSTs an Activity with a JWT in the Authorization header, not a Kong stamp or an HMAC-over-body signature, so the route's gate rejected it before the adapter ran.

Fix (kept generic — no Teams-specific branch in the route)

• TeamsAdapter.handle_webhook(body, auth_header) — deserializes the Activity and hands it to process_activity(), which validates the JWT fail-closed. Sets webhook_self_authenticates = True.
• Generic route (flask_integration.py) — an adapter that sets webhook_self_authenticates is True opts out of the Kong/HMAC gate (it authenticates itself), and the route now maps an auth_header/authorization param to the Authorization header. Strict identity check (is True) so a truthy stand-in can never silently disable the gate.

Any future bearer-JWT channel reuses the same seam — no new bespoke code.

Out of scope (deliberately)

WhatsApp is unchanged. Its Baileys gateway is a persistent WhatsApp-Web connection, not an HTTP webhook, so it can't be folded onto this path without breaking it — it stays a documented exception.

Tests

Adds two regression cases: (1) a self-authenticating adapter bypasses the gate and its handle_webhook receives the Authorization header; (2) a truthy-but-not-True flag must NOT bypass the gate. Full file: 25 passed.