DO NOT MERGE before Phase A.5 — compose: network_mode: host + Paliadin env vars

Stages the docker-compose.yml change so m can flip it together with
the Phase A.5 traefik validation (design §7). Three deltas:

1. network_mode: host on the web service. paliad inherits mLake's
   tailnet interface so the Go RemotePaliadinService can reach
   mRiver:22022 over Tailscale.

2. Removed the now-meaningless `expose: ["8080"]` block (host-mode
   binds the port on the host directly).

3. Five new env entries plumbing the Paliadin remote-routing knobs:
   PALIADIN_REMOTE_HOST=100.99.98.203
   PALIADIN_REMOTE_PORT=22022
   PALIADIN_REMOTE_USER=m
   PALIADIN_SSH_PRIVATE_KEY=...   (multi-line; register as Dokploy secret)
   PALIADIN_KNOWN_HOSTS=...       (one-line; register as Dokploy secret)

   The two secret values are staged at ~/.paliad-staging/ on mRiver
   from Phase A.0 — see issue #12 issuecomment-6886.

**This commit must NOT merge to main until Phase A.5 confirms traefik
still routes paliad.de under host mode.** Per the design's §4.2
honest trade-off acknowledgement: if the test surfaces M1 (traefik
can't discover via Docker DNS → 502), revert this commit and revisit
decision 1 (sidecar variant) in a follow-up issue. Per maria's
non-negotiable head rule, m drives the merge.

A.5 procedure (m's hands):
1. Branch this commit (or cherry-pick onto a temp branch off main)
2. Push to trigger Dokploy redeploy
3. curl --connect-timeout 5 -sSI https://paliad.de/
4. PASS (200/3xx): keep the merge; register Dokploy secrets; redeploy
5. FAIL (502): git revert HEAD && git push; file follow-up issue

Refs m/paliad#12

docker-compose.yml

@@ -1,8 +1,14 @@
 services:
   web:
     build: .
-    expose:
+    # network_mode: host so paliad inherits mLake's tailscale0 interface
-      - "8080"
+    # and can reach mRiver (100.99.98.203) for the Paliadin remote route
+    # (t-paliad-151). With host mode, `expose` is meaningless — paliad
+    # listens on host port 8080 directly. traefik routing under host mode
+    # is gated by Phase A.5 (see docs/design-paliadin-tailscale-ssh-2026
+    # -05-07.md §4.2 + §7); if that test fails, revert this commit and
+    # revisit decision 1.
+    network_mode: host
     environment:
       - PORT=8080
       - SUPABASE_URL=${SUPABASE_URL}
@@ -20,5 +26,16 @@ services:
       - SMTP_FROM=${SMTP_FROM}
       - SMTP_FROM_NAME=${SMTP_FROM_NAME}
       - SMTP_USE_TLS=${SMTP_USE_TLS}
+      # Paliadin remote routing (t-paliad-151). When PALIADIN_REMOTE_HOST
+      # is set, paliad forwards each turn to mRiver via SSH on port 22022
+      # (Tailscale-SSH bypass, see design §4.5). Without these vars,
+      # paliad falls back to local tmux (or DisabledPaliadinService).
+      # The PRIVATE_KEY and KNOWN_HOSTS values are multi-line — register
+      # them in Dokploy as secret env vars, not in plain compose text.
+      - PALIADIN_REMOTE_HOST=${PALIADIN_REMOTE_HOST}
+      - PALIADIN_REMOTE_PORT=${PALIADIN_REMOTE_PORT}
+      - PALIADIN_REMOTE_USER=${PALIADIN_REMOTE_USER}
+      - PALIADIN_SSH_PRIVATE_KEY=${PALIADIN_SSH_PRIVATE_KEY}
+      - PALIADIN_KNOWN_HOSTS=${PALIADIN_KNOWN_HOSTS}
       # - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY}  # Phase H (AI Frist-Extraktion), currently deferred
     restart: unless-stopped