feat(12-02): OIDC boot env-OR-app_config fallback + pre-auth mount verification

- A2 CONFIRMED: @hono/oidc-auth reads OIDC_ISSUER/OIDC_CLIENT_ID/OIDC_AUTH_EXTERNAL_URL
  at per-request call time (env(c) → process.env), NOT at import time — fresh instance
  boots cleanly without OIDC env vars
- Implement oidcConfigFallbackMiddleware in auth/middleware.ts: reads OIDC_ISSUER,
  OIDC_CLIENT_ID, OIDC_AUTH_EXTERNAL_URL from app_config when process.env is absent,
  injects into process.env before oidcAuthMiddleware() reads it (D-02/D-03/Recommendation a)
- Mount oidcConfigFallbackMiddleware before oidcAuthMiddleware() in index.ts so
  wizard-configured instances work before a container restart
- Verify /api/setup mount order: line 49 < devAuthBypass line 54 (T-12-09/Pitfall 1)
- Fix push.test.ts vi.doMock for middleware.js: add oidcConfigFallbackMiddleware stub
- 394 tests pass | 5 todo (D-08 RED scaffolds); typecheck clean

apps/api/src/auth/middleware.ts

@@ -11,6 +11,20 @@
  *   OIDC_REDIRECT_URI         — https://familysync.<domain>/callback
  *   OIDC_AUTH_EXTERNAL_URL    — https://familysync.<domain> — MANDATORY behind Pangolin (Pitfall 1)
  *
+ * Phase 12 — env-OR-app_config fallback (D-02 / D-03 / Recommendation a):
+ *   OIDC_ISSUER, OIDC_CLIENT_ID, OIDC_AUTH_EXTERNAL_URL may be absent from env on a
+ *   fresh unconfigured instance or when the wizard has written them to app_config but
+ *   the container has not yet been restarted. oidcAuthMiddlewareWithFallback() reads
+ *   the process.env value first; when absent, reads the app_config DB value and injects
+ *   it via process.env for the duration of the request. This avoids a crash on fresh
+ *   boot and allows wizard-configured values to work before a container restart.
+ *
+ *   A2 CONFIRMED: @hono/oidc-auth reads OIDC_ISSUER etc. at per-request call time
+ *   (inside setOidcAuthEnv → env(c) → process.env). NOT at import time. A fresh instance
+ *   without these env vars boots cleanly; the HTTP 500 only occurs if a request hits
+ *   /api/* OIDC-protected routes before setup is complete — which is acceptable since
+ *   /api/setup/* is pre-auth and is the only pre-setup surface.
+ *
  * Session persistence (AUTH-02):
  *   @hono/oidc-auth stores the refresh token in the signed JWT cookie.
  *   Every OIDC_AUTH_REFRESH_INTERVAL (default 15 min) the middleware calls
@@ -23,4 +37,57 @@
  * Source: https://github.com/honojs/middleware/tree/main/packages/oidc-auth
  */
 
+import type { Context, Next } from 'hono';
+import { eq } from 'drizzle-orm';
+import { db } from '../db/client.js';
+import { appConfig } from '../db/schema.js';
+
 export { oidcAuthMiddleware, processOAuthCallback, getAuth } from '@hono/oidc-auth';
+
+// ---------------------------------------------------------------------------
+// env-OR-app_config fallback middleware (D-02 / D-03 / Recommendation a)
+//
+// OIDC_ISSUER, OIDC_CLIENT_ID, OIDC_AUTH_EXTERNAL_URL are non-secret config
+// (D-01) that the wizard writes to app_config. When the env var is absent,
+// this middleware reads the app_config value and sets it into process.env so
+// that the downstream oidcAuthMiddleware() picks it up from its env(c) read.
+//
+// Env floor vars that stay in env only (never in app_config):
+//   OIDC_AUTH_SECRET, OIDC_CLIENT_SECRET — secrets; must be in Docker env (D-01)
+//
+// Called once per /api/* request that reaches the OIDC guard.
+// Reading 3 app_config rows adds negligible overhead for a 2-person household app.
+// ---------------------------------------------------------------------------
+
+export async function oidcConfigFallbackMiddleware(c: Context, next: Next): Promise<void> {
+  const needsIssuer = !process.env.OIDC_ISSUER;
+  const needsClientId = !process.env.OIDC_CLIENT_ID;
+  const needsExternalUrl = !process.env.OIDC_AUTH_EXTERNAL_URL;
+
+  if (needsIssuer || needsClientId || needsExternalUrl) {
+    // Build a minimal list of keys to read — only the absent ones
+    const keysToRead: string[] = [];
+    if (needsIssuer) keysToRead.push('oidc_issuer');
+    if (needsClientId) keysToRead.push('oidc_client_id');
+    if (needsExternalUrl) keysToRead.push('app_external_url');
+
+    // Read from app_config (written by POST /api/setup/config)
+    for (const key of keysToRead) {
+      const [row] = await db
+        .select({ value: appConfig.value })
+        .from(appConfig)
+        .where(eq(appConfig.key, key))
+        .limit(1);
+
+      if (row?.value) {
+        // Inject into process.env so oidcAuthMiddleware()'s env(c) picks it up
+        // This is safe: these are non-secret, app-config-owned values (D-01)
+        if (key === 'oidc_issuer') process.env.OIDC_ISSUER = row.value;
+        if (key === 'oidc_client_id') process.env.OIDC_CLIENT_ID = row.value;
+        if (key === 'app_external_url') process.env.OIDC_AUTH_EXTERNAL_URL = row.value;
+      }
+    }
+  }
+
+  await next();
+}