User page: hash-routed view, full block hash, aligned rewards

The per-user view was an overlay modal, but users asked for an
actual page — focused, scrollable, addressable. Replace the modal
with a hash-routed page: selectUser(addr) sets window.location.hash
to #/user/<addr> and a hashchange listener syncs the selection
state back, so browser back/forward and direct-link refresh all
work without a routing library. App renders the dashboard or the
UserDetailPage based on selection.user.

Make the clickable BTC addresses in the Miners table obviously
interactive: accent colour, always-on dashed underline, brighter on
hover/focus. The previous styling rendered them as dim static text
with a hover underline, so it wasn't obvious they were links.

BlocksTable: show the full 64-char block hash as a link to
mempool.space (auto-picks testnet4/signet based on snap.chain).
word-break: break-all keeps the hash from blowing out the column
width. Reward column is split into a tabular-num number span and a
dim 0.75em "BTC" unit span, matching the Block reward tile in the
overview, so numbers line up cleanly across rows.

ui/src/stores/selection.svelte.ts

@@ -1,13 +1,49 @@
-// Cross-component selection state. Currently just tracks the user
-// whose detail modal is open; App renders the modal off this store
-// so any component in the tree can open it by setting `user`.
+// Simple hash-based routing for user pages. The URL hash is the
+// source of truth:
+//   #/                -> dashboard
+//   #/user/<address>  -> per-user page
+//
+// selectUser / clearSelection just mutate the hash; a hashchange
+// listener reads it back into reactive state so any component in the
+// tree re-renders when the route changes.
 
-export const selection = $state<{ user: string | null }>({ user: null });
+const USER_PREFIX = "#/user/";
+
+export const selection = $state<{ user: string | null }>({
+  user: readHash(),
+});
+
+function readHash(): string | null {
+  if (typeof window === "undefined") return null;
+  const h = window.location.hash;
+  if (h.startsWith(USER_PREFIX)) {
+    const addr = decodeURIComponent(h.slice(USER_PREFIX.length));
+    return addr || null;
+  }
+  return null;
+}
+
+function syncFromHash(): void {
+  selection.user = readHash();
+}
+
+if (typeof window !== "undefined") {
+  window.addEventListener("hashchange", syncFromHash);
+}
 
 export function selectUser(address: string): void {
-  selection.user = address;
+  // Set the hash; the hashchange listener updates selection.user so
+  // routing-style state stays in one place.
+  window.location.hash = USER_PREFIX + encodeURIComponent(address);
 }
 
 export function clearSelection(): void {
-  selection.user = null;
+  // Prefer history.back when we arrived here via selectUser so the
+  // browser back arrow does the obvious thing; otherwise just drop
+  // the hash so a fresh page load starts on the dashboard.
+  if (window.history.length > 1 && window.location.hash.startsWith(USER_PREFIX)) {
+    window.history.back();
+  } else {
+    window.location.hash = "";
+  }
 }