fix(ess-pro/compose): align with matrix-stack 26.6.1 and fix routing/security gaps

Verified the role against the real matrix-stack Helm chart (pulled 26.6.1)
and fixed divergences found during review.

Bugs:
- Add MAS OIDC discovery router: /.well-known/openid-configuration must hit
  the MAS root listener (8082), not web (8080) — was 404, breaking OIDC login
- Add Synapse ip_range_blacklist (full SSRF blocklist for all outbound
  federation/identity requests; previously only url-preview blacklist present)
- Make federation_client_minimum_tls_version unconditional (chart sets it in
  shared-underrides; role only set it when federation was enabled)
- Restart only rendered fed-reader replicas in the handler instead of the
  whole compose project (missing services: filter)

Chart alignment (26.5.1 -> 26.6.1):
- Bump chart version and all image tags (mas -> matrix-authentication-service
  -pro:1.18.0, postgres 17, synapse v1.154.0-pro.1, element-web v1.12.21, etc.)
- redis maxmemory 256mb -> chart default 40mb (configurable)
- Add element-web map_style_url (configurable)

Hardening / hygiene:
- Validate ess_rtc_external_ip is a real IP (regex, no extra collection dep)
- Read admin password from the in-container secret file instead of passing it
  on the host process list during mas-cli register-user
- apt cache_valid_time, postgres first-boot-only comment, haproxy failover note
- Add meta/argument_specs.yml documenting all public variables
- README: chart version, service count, OIDC discovery verification step

Signed-off-by: Simon Bärlocher <simon@whatwedo.ch>

roles/ess_pro_compose/templates/synapse/homeserver.yaml.j2

@@ -18,6 +18,33 @@ log_config: "/conf/log_config.yaml"
 enable_metrics: true
 report_stats: false
 
+# Minimum TLS for outbound federation (chart: shared-underrides, always on).
+federation_client_minimum_tls_version: '1.2'
+
+# SSRF protection for ALL outbound requests (federation, identity, etc.).
+# Distinct from url_preview_ip_range_blacklist below. Verbatim from chart
+# synapse-04-homeserver-overrides.
+ip_range_blacklist:
+  - '127.0.0.0/8'
+  - '10.0.0.0/8'
+  - '172.16.0.0/12'
+  - '192.168.0.0/16'
+  - '100.64.0.0/10'
+  - '192.0.0.0/24'
+  - '169.254.0.0/16'
+  - '192.88.99.0/24'
+  - '198.18.0.0/15'
+  - '192.0.2.0/24'
+  - '198.51.100.0/24'
+  - '203.0.113.0/24'
+  - '224.0.0.0/4'
+  - '::1/128'
+  - 'fe80::/10'
+  - 'fc00::/7'
+  - '2001:db8::/32'
+  - 'ff00::/8'
+  - 'fec0::/10'
+
 # ---- Listeners (from 05-main.yaml) ----------------------------------------
 listeners:
   - port: 8008
@@ -130,7 +157,6 @@ url_preview_ip_range_blacklist:
 # ---- Federation -----------------------------------------------------------
 {% if ess_enable_federation %}
 send_federation: true
-federation_client_minimum_tls_version: '1.2'
 {% else %}
 send_federation: false
 federation_domain_whitelist: []