feat(web): split SPA from oikos binary, require auth on every route

Phase 0 of plans/2026-07-12-wails-desktop-app.md. The control-room SPA
is no longer embedded (web/embed.go deleted); it's a standalone static
build served separately (make ui / make deploy-ui). The api process
adds CORS and drops the dev-open auth bypass — every route now needs a
real bearer token, including SSE (?token= query param, EventSource
can't set headers) and api's own /agent proxy to nomos (previously
unauthenticated by omission).

nomos was an unauthenticated client of api's /mcp and approval-decision
endpoints; closing dev-open would have broken it, so it now sends
Authorization: Bearer $OIKOS_MCP_BEARER_TOKEN on every call back to api.

SPA gets a runtime config module (config.ts) and a Config.svelte
first-launch/reconfigure page, reachable afterwards via a "Connection"
entry in the sidebar footer. Every fetch() in api.ts routes through
fetchWithAuth so the same build works same-origin (browser prod, Vite
dev proxy) or cross-origin (future Wails webview, remote access).

Six gaps found against the plan and the live Caddy topology while
implementing — documented in the plan's "Plan review" section, most
notably: api's own /agent mount was never behind combinedAuth (fixed),
and production's Authentik forward-auth needs a bearer-token bypass for
API routes that this repo's Caddyfile.oikos reference copy now has, but
the real dtoro/caddy-conf deploy does not yet.

Verified live: cross-origin static SPA + API, CORS, bearer auth, SSE
query-token auth, and localStorage persistence all confirmed working
in-browser. Full Go test suite and npm run build pass with no
regressions against the pre-change baseline.

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

internal/config/config.go

@@ -24,6 +24,11 @@ type Config struct {
 	OIDCIssuer     string // OIDC issuer URL for JWT validation (e.g. https://authentik.example.com/application/o/oikos/)
 	OIDCClientID   string // OIDC client ID (aud claim expected in JWT)
 
+	// CORS (client/server split — see plans/2026-07-12-wails-desktop-app.md
+	// 0.3). Needed for the Wails webview and local dev (Vite on a different
+	// port than the API); a no-op when the SPA and API share an origin.
+	CORSAllowedOrigin string
+
 	// Observability
 	Debug bool // verbose logging, probe payloads, SQL
 
@@ -73,6 +78,7 @@ func Default() Config {
 		DatabaseURL:       "postgres://oikos:***@localhost:5432/oikos?sslmode=disable",
 		APIListen:         ":8090",
 		APIEnv:            "dev",
+		CORSAllowedOrigin: "*",
 		SeedsDir:          "seeds",
 		MigrationsDir:     "migrations",
 		SchedulerInterval: 30 * time.Second,
@@ -108,6 +114,9 @@ func FromEnv() Config {
 	if v := os.Getenv("OIKOS_MCP_BEARER_TOKEN"); v != "" {
 		c.MCPBearerToken = v
 	}
+	if v := os.Getenv("OIKOS_CORS_ORIGIN"); v != "" {
+		c.CORSAllowedOrigin = v
+	}
 	if v := os.Getenv("OIKOS_SEEDS_DIR"); v != "" {
 		c.SeedsDir = v
 	}