0.28.0 — operational hardening (plan D1–D5): CI deploy gate, versioned images, rate limiting, resource limits, health probes

D1: deploy.sh CI gate — read-only SHA via git ls-remote, Gitea commit-status
    poll, portable mkdir deploy lock (macOS, no flock), TOCTOU guard, token
    passed via curl --config - (not argv), graceful misconfig tolerance.
D2: version-tagged images — OIKOS_VERSION=v$VERSION, keep-last-3 prune derived
    from 'docker compose config --images'; VERSION read after pull.
D3: per-IP rate limiting — new internal/httpapi/ratelimit.go (x/time/rate),
    rightmost-XFF, /healthz exempt, ctx-driven sweep; disabled by default.
D4: mem_limit/cpus on all 10 compose services.
D5: staleness-aware health probes — new internal/health package wired into
    scheduler (:8093) and notifier (:8094); nomos already had :8092.

Two /review passes hardened the deploy lock, TOCTOU guard, token hygiene,
and XFF handling.

internal/config/config.go

@@ -30,6 +30,17 @@ type Config struct {
 	// port than the API); a no-op when the SPA and API share an origin.
 	CORSAllowedOrigin string
 
+	// Rate limiting (plan D3). APIRateLimit is the per-IP requests/sec cap;
+	// APIRateBurst is the token-bucket burst (defaults to 2x the limit when
+	// unset). A limit of 0 disables rate limiting entirely.
+	APIRateLimit int
+	APIRateBurst int
+
+	// Health probe HTTP listener (plan D5). Background-loop roles (scheduler,
+	// notifier) expose a staleness-aware /healthz here. Empty disables the
+	// health server (local/non-docker runs).
+	HealthListen string
+
 	// Observability
 	Debug bool // verbose logging, probe payloads, SQL
 
@@ -121,6 +132,11 @@ func FromEnv() Config {
 	if v := os.Getenv("OIKOS_CORS_ORIGIN"); v != "" {
 		c.CORSAllowedOrigin = v
 	}
+	c.APIRateLimit = parseInt(os.Getenv("OIKOS_API_RATE_LIMIT"))
+	c.APIRateBurst = parseInt(os.Getenv("OIKOS_API_RATE_BURST"))
+	if v := os.Getenv("OIKOS_HEALTH_LISTEN"); v != "" {
+		c.HealthListen = v
+	}
 	if v := os.Getenv("OIKOS_SEEDS_DIR"); v != "" {
 		c.SeedsDir = v
 	}