Remove legacy question storage (#7)

Deletes obsolete question/answer/vote persistence and the compatibility answer endpoint. Existing databases drop the legacy tables through migration 009. Plumber replies now notify the root homeowner even when nested beneath another plumber reply. Post and reply forms prevent duplicate submissions and show progress while posting.

Reviewed-on: #7
Co-authored-by: codegirl-007 <s.raide@gmail.com>

static/app.css

@@ -41,6 +41,31 @@ body {
   background-size: 100% 100%, 48px 48px;
 }
 
+.submit-progress {
+  position: fixed;
+  inset: 0 0 auto;
+  z-index: 100;
+  height: 3px;
+  overflow: hidden;
+  pointer-events: none;
+}
+
+.submit-progress[hidden] { display: none; }
+
+.submit-progress-bar {
+  display: block;
+  width: 35%;
+  height: 100%;
+  background: var(--signal);
+  box-shadow: 0 0 12px var(--signal);
+  animation: submit-progress 900ms ease-in-out infinite;
+}
+
+@keyframes submit-progress {
+  from { transform: translateX(-100%); }
+  to { transform: translateX(300%); }
+}
+
 img, svg { display: block; }
 
 a {
@@ -253,6 +278,12 @@ a {
 
 .btn-primary:hover { filter: brightness(1.08); }
 
+.btn:disabled {
+  cursor: wait;
+  opacity: 0.65;
+  filter: none;
+}
+
 .btn-ghost {
   background: transparent;
   color: var(--ink);
@@ -763,6 +794,10 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
 
 @media (prefers-reduced-motion: reduce) {
   .btn-primary:hover { filter: none; }
+  .submit-progress-bar {
+    width: 100%;
+    animation: none;
+  }
 }
 
 .admin-users { margin-top: 20px; overflow-x: auto; }