Add self-hosted RCS backend, extension, and ops tooling

Ship the Go/SQLite API and Web UI, Chrome/Brave capture addon,
Docker Compose, Pangolin reverse-proxy support, and a user-crontab
watchdog so the binary stays running without systemd.

backend/internal/web/static/app.js

@@ -0,0 +1,61 @@
+document.querySelectorAll(".copy-url").forEach((button) => {
+  button.addEventListener("click", async () => {
+    const url = button.getAttribute("data-url");
+    if (!url) return;
+    try {
+      await navigator.clipboard.writeText(url);
+      const hint = button.parentElement.querySelector(".copied-hint");
+      if (hint) {
+        hint.hidden = false;
+        setTimeout(() => {
+          hint.hidden = true;
+        }, 1500);
+      }
+    } catch (err) {
+      console.error("copy failed", err);
+    }
+  });
+});
+
+(function setupLightbox() {
+  const lightbox = document.getElementById("lightbox");
+  const lightboxImg = document.getElementById("lightbox-img");
+  if (!lightbox || !lightboxImg) {
+    console.warn("[RCS] lightbox elements missing");
+    return;
+  }
+
+  function openLightbox(src) {
+    lightboxImg.src = src;
+    lightbox.hidden = false;
+    lightbox.setAttribute("aria-hidden", "false");
+    document.body.classList.add("lightbox-open");
+  }
+
+  function closeLightbox() {
+    lightbox.hidden = true;
+    lightbox.setAttribute("aria-hidden", "true");
+    lightboxImg.removeAttribute("src");
+    document.body.classList.remove("lightbox-open");
+  }
+
+  // Event delegation so thumbs work even if markup is re-rendered later.
+  document.addEventListener("click", (event) => {
+    const thumb = event.target.closest(".shot-thumb");
+    if (thumb) {
+      event.preventDefault();
+      const src = thumb.getAttribute("data-full") || (thumb.querySelector("img") && thumb.querySelector("img").src);
+      if (src) openLightbox(src);
+      return;
+    }
+    if (event.target === lightbox || event.target.classList.contains("lightbox-close")) {
+      closeLightbox();
+    }
+  });
+
+  document.addEventListener("keydown", (event) => {
+    if (event.key === "Escape" && !lightbox.hidden) {
+      closeLightbox();
+    }
+  });
+})();