feat(appservice): mosaic-as daemon host + container (M4a deploy prep, agent-comms#9)

apps/appservice: framework-agnostic node:http daemon hosting
@mosaicstack/appservice — Synapse transactions endpoint passthrough,
internal bridge API v1 (messages/typing) with HMAC-digest timing-safe
bearer tokens, 1MiB request body cap, explicit 405 inside the
authenticated bridge block (no fall-through around auth), health endpoint,
env config, registration YAML printer bin. docker/appservice.Dockerfile
mirrors the gateway multi-stage pnpm/turbo pattern, runs as USER node
with container healthcheck. 9 vitest tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -39,6 +39,25 @@ importers:
         specifier: ^2.0.0
         version: 2.1.9(@types/node@24.12.0)(jsdom@29.0.0(@noble/hashes@2.0.1))(lightningcss@1.31.1)
 
+  apps/appservice:
+    dependencies:
+      '@mosaicstack/appservice':
+        specifier: workspace:*
+        version: link:../../packages/appservice
+    devDependencies:
+      '@types/node':
+        specifier: ^22.0.0
+        version: 22.19.15
+      tsx:
+        specifier: ^4.19.0
+        version: 4.21.0
+      typescript:
+        specifier: ^5.8.0
+        version: 5.9.3
+      vitest:
+        specifier: ^2.0.0
+        version: 2.1.9(@types/node@22.19.15)(jsdom@29.0.0(@noble/hashes@2.0.1))(lightningcss@1.31.1)
+
   apps/gateway:
     dependencies:
       '@anthropic-ai/sdk':