Add nested posts UI (#5)

## Summary
- Cut hunt, question, submission, voting, hiding, and profile flows over to unified posts
- Render nested replies with permission-aware inline Reply/Edit controls and edited markers
- Add post profile queries and the author index migration they depend on

Co-authored-by: codegirl-007 <s.raide@gmail.com>

static/app.css

@@ -552,12 +552,14 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
   padding: 18px 14px;
 }
 
+.post-content { min-width: 0; }
+
 .question-page h1 {
   font-size: clamp(1.5rem, 3.5vw, 2.1rem);
   line-height: 1.15;
 }
 
-.q-body, .answer-body {
+.post-body {
   white-space: pre-wrap;
   margin: 14px 0 0;
   text-wrap: pretty;
@@ -574,18 +576,7 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
 }
 .crumb a:hover { color: var(--signal); }
 
-.answer {
-  margin-top: 16px;
-  padding: 20px 18px;
-  background: var(--panel);
-  border: 1px solid var(--line);
-}
-
-.answer.is-in {
-  border-color: var(--signal);
-}
-
-.answer-kicker {
+.post-kicker {
   margin: 0 0 6px;
   font-family: var(--mono);
   text-transform: uppercase;
@@ -595,27 +586,99 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
   color: var(--signal);
 }
 
-.answer h2 {
-  margin: 0;
-  font-size: 1.15rem;
-  font-weight: 500;
-  letter-spacing: 0.04em;
-  text-transform: uppercase;
+.conversation {
+  margin-top: 32px;
 }
 
-.byline {
+.conversation-head {
+  margin-bottom: 12px;
+  padding-bottom: 12px;
+  border-bottom: 1px solid var(--line);
+}
+
+.conversation h2 {
+  margin: 0;
+  font-size: 1.25rem;
+  font-weight: 500;
+}
+
+.conversation-head .eyebrow {
+  margin-bottom: 5px;
+}
+
+.thread {
+  display: grid;
+  gap: 12px;
+}
+
+.thread-post {
+  position: relative;
+  padding: 16px;
+  background: var(--panel);
+  border: 1px solid var(--line);
+  border-left: 2px solid var(--zinc);
+  overflow-wrap: anywhere;
+}
+
+.thread-post.is-shop {
+  border-left-color: var(--signal);
+}
+
+.thread-post:target,
+.q-detail:target {
+  outline: 2px solid var(--signal);
+  outline-offset: 3px;
+}
+
+.thread-post-branch,
+.thread-post-deep {
+  margin-left: clamp(12px, 4vw, 28px);
+}
+
+.thread-post-deep .thread-post-deep {
+  margin-left: 0;
+}
+
+.post-replies {
+  display: grid;
+  gap: 12px;
+  margin-top: 12px;
+}
+
+.post-meta {
   margin: 6px 0 0;
   color: var(--muted);
   font-family: var(--mono);
   font-size: 0.72rem;
 }
 
-.answer-editor {
-  margin-top: 16px;
+.edited {
+  display: inline-block;
+  margin-left: 8px;
+  color: var(--zinc);
+  font-size: 0.65rem;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+}
+
+.post-actions {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: flex-start;
+  gap: 0 16px;
+  margin-top: 10px;
   border-top: 1px solid var(--line);
 }
 
-.answer-editor summary {
+.post-composer {
+  min-width: 0;
+}
+
+.post-composer[open] {
+  flex: 1 0 100%;
+}
+
+.post-composer summary {
   display: flex;
   width: fit-content;
   min-height: 44px;
@@ -630,23 +693,34 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
   list-style: none;
 }
 
-.answer-editor summary::-webkit-details-marker { display: none; }
-.answer-editor summary:hover,
-.answer-editor[open] summary { color: var(--signal); }
-.answer-editor summary:focus-visible {
+.post-composer summary::-webkit-details-marker { display: none; }
+.post-composer summary::marker { content: ""; }
+.post-composer summary:hover,
+.post-composer[open] summary { color: var(--signal); }
+.post-composer summary:focus-visible {
   outline: 2px solid var(--signal);
   outline-offset: 2px;
 }
 
-.answer-editor .answer-form { margin-top: 4px; }
+.post-form {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  width: 100%;
+  margin: 0 0 14px;
+}
 
-.answer-form-actions {
+.post-form-actions {
   display: flex;
   flex-wrap: wrap;
   gap: 8px;
 }
 
-.answer-form-actions .btn { flex: 1 1 10rem; }
+.post-form-actions .btn { flex: 1 1 10rem; }
+
+.post-hide {
+  margin: 0;
+}
 
 .waiting { color: var(--muted); margin: 0; font-family: var(--mono); font-size: 0.8rem; }