Home mosaic, multi-select delete, offline banner and loading states

- Home puts the dashboards beside the flows: two equal-height columns,
  capped and scrollable, most recently worked on first. Each tile is a
  schematic footprint built from the stored widget placements.
- Flows and dashboards can be picked by long press or ctrl-click; the
  create button becomes a trash and one dialog covers the batch.
- The offline banner is drawn on the body so it centres on the viewport,
  and the live socket now releases the offline latch a stray 503 set.
- A boot spinner before React's first commit, a router pending screen for
  code-split pages, and skeletons where an empty list used to flash.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tULRZJUkZsw7rMJ3h4xvu

frontend/src/lib/connectionStore.ts

@@ -16,6 +16,16 @@ type Connection = {
 }
 
 let state: Connection = { offline: false, lastSeen: null }
+/**
+ * Whether the live socket is up right now.
+ *
+ * The socket is the continuous signal; a failed request is only a lagging one.
+ * Latching `offline` on a single refused request is what used to leave the
+ * banner up for good: the socket had never dropped, so no reconnect was coming
+ * to clear it, and nothing else on a quiet page refetches. Reloading was the
+ * only way out.
+ */
+let socketOpen = false
 const listeners = new Set<() => void>()
 
 function emit(next: Connection) {
@@ -28,6 +38,10 @@ function emit(next: Connection) {
 
 export const connectionStore = {
   setOffline(lastSeen: string | number | null) {
+    // The socket is up, so the installation is reachable: this was one bad
+    // answer rather than a lost tunnel, and the banner would have nothing to
+    // take it back down again.
+    if (socketOpen) return
     const at =
       typeof lastSeen === "string"
         ? Date.parse(lastSeen)
@@ -39,6 +53,17 @@ export const connectionStore = {
   setOnline() {
     emit({ offline: false, lastSeen: null })
   },
+  /**
+   * The live socket opened or closed.
+   *
+   * An open socket is proof the installation can be heard, so it also clears
+   * the banner — and since the socket reconnects on its own, that is the one
+   * release the offline state can always count on.
+   */
+  setSocketOpen(open: boolean) {
+    socketOpen = open
+    if (open) emit({ offline: false, lastSeen: null })
+  },
   subscribe(listener: () => void) {
     listeners.add(listener)
     return () => listeners.delete(listener)