fix: inject db context for /s/* short share URL route

The /s/:token route was registered outside the /api/* db middleware
scope, causing db to be undefined and a 500 error on share link access.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/index.ts

@@ -135,6 +135,10 @@ app.use("/api/*", async (c, next) => {
 	c.set("db", prodDb);
 	return next();
 });
+app.use("/s/*", async (c, next) => {
+	c.set("db", prodDb);
+	return next();
+});
 
 // Rate limiting for public endpoints (per D-07, D-08)
 const browseTier = createRateLimit(120, 60_000);