Add zulip-oidc-redirect-fix prose contract

Fixes Zulip OIDC authentication where redirect_uri used internal IP
(192.168.68.19) instead of public domain (chat.sysloggh.net) after
server restart. Monkey-patches social_core.strategy.BaseStrategy
to use ROOT_DOMAIN_URI for all redirect URI construction.

zulip-oidc-redirect-fix.prose.md

@@ -0,0 +1,92 @@
+---
+kind: responsibility
+name: zulip-oidc-redirect-fix
+status: active
+description: >
+  Fixes Zulip OIDC authentication when the redirect_uri sent to Authentik
+  uses the internal IP (192.168.68.19) instead of the public domain
+  (chat.sysloggh.net). Applied via monkey-patch in ZULIP_CUSTOM_SETTINGS.
+  Survives container restarts through compose.override.yaml.
+agent: abiba
+triggers:
+  - Zulip OIDC login returns "Redirect URI Error" from Authentik
+  - redirect_uri in OAuth URL shows 192.168.68.19 instead of chat.sysloggh.net
+  - After Zulip server restart, Authentik SSO login broken
+---
+
+## Maintains
+
+- zulip-oidc: { redirect_uri: "https://chat.sysloggh.net/complete/oidc/", scheme: "https", host: "chat.sysloggh.net" }
+- authentik-acceptance: { status: "accepted" | "rejected" }
+- patched-strategy: { module: "social_core.strategy.BaseStrategy", method: "absolute_uri", root: "ROOT_DOMAIN_URI" }
+
+## Detection
+
+### Rule 1: Wrong redirect_uri host
+- **Detect**: `curl -sk -L "https://chat.sysloggh.net/accounts/login/social/oidc/authentik" 2>&1 | grep "redirect_uri=https://192.168.68.19"`
+- **Status**: CRITICAL — Authentik will reject
+- **Trigger fix** → Execute self-heal
+
+### Rule 2: OIDC flow broken
+- **Detect**: `curl -sk -o /dev/null -w "%{http_code}" "https://chat.sysloggh.net/accounts/login/social/oidc/authentik"` → chain ends at Authentik 400
+- **Diagnose**: Check redirect_uri in the 302 Location header chain
+
+## Fix (Self-Heal)
+
+Two layers applied:
+
+### Layer 1: Live patch (inside container, immediate)
+```bash
+# Add to /home/zulip/deployments/current/zproject/computed_settings.py:
+SOCIAL_AUTH_REDIRECT_IS_HTTPS = True
+
+import urllib.parse
+from social_core.strategy import BaseStrategy
+_original_absolute_uri = BaseStrategy.absolute_uri
+def _patched_absolute_uri(self, path=None):
+    from django.conf import settings
+    root = getattr(settings, "ROOT_DOMAIN_URI", "https://chat.sysloggh.net")
+    if path is not None:
+        return urllib.parse.urljoin(root, path)
+    return root
+BaseStrategy.absolute_uri = _patched_absolute_uri
+
+# Restart Django
+supervisorctl restart zulip-django
+```
+
+### Layer 2: Persistent fix (compose.override.yaml)
+The patch is baked into the `ZULIP_CUSTOM_SETTINGS` env var in
+`/opt/zulip/compose.override.yaml`. Survives Docker container restarts.
+
+### Verification
+```bash
+STEP1=$(curl -sk -w "%{redirect_url}" \
+  "https://chat.sysloggh.net/accounts/login/social/oidc/authentik" -o /dev/null)
+curl -sk -D- "$STEP1" -o /dev/null 2>&1 | grep "redirect_uri="
+# Expected: redirect_uri=https://chat.sysloggh.net/complete/oidc/
+# Wrong:    redirect_uri=https://192.168.68.19/complete/oidc/
+```
+
+### Rollback
+Remove the patch block from `compose.override.yaml` and restart the container:
+```bash
+docker compose -f /opt/zulip/compose.yaml -f /opt/zulip/compose.override.yaml up -d zulip
+```
+
+## Root Cause
+
+After Zulip restart, `social-auth-core` computes the OIDC `redirect_uri` via
+Django's `request.build_absolute_uri()` → `request.get_host()`. The upstream
+Netbird/Traefik proxy (72.61.0.17) forwards `Host: 192.168.68.19` instead of
+`Host: chat.sysloggh.net`, and without `HTTP_HOST` in nginx's `uwsgi_params`,
+Django falls back to the server's IP.
+
+The monkey-patch overrides `BaseStrategy.absolute_uri()` to always use
+`ROOT_DOMAIN_URI` (`https://chat.sysloggh.net`) regardless of the request's
+Host header.
+
+## Related Contracts
+
+- `zulip-health.prose.md` — General Zulip health monitoring
+- `zulip-self-heal.prose.md` — RETIRED (pi extension removed)