feat: remove quick reply, streamline blog reply (v2.7.0)

Remove the quick-reply code path entirely — all replies now go through
Micropub as blog posts. Quick replies created orphan URLs that served
raw JSON-LD to browsers and caused unreadable links in conversations.

- Delete quick-reply controller (note-object.js) and route
- Remove ap_notes collection registration
- Simplify compose form: no mode toggle, no character counter
- Remove quick-reply CSS and locale strings

Confab-Link: http://localhost:8080/sessions/d116ad5b-ef8a-424e-9ebe-76c06bef1df6

assets/reader.css

@@ -976,34 +976,6 @@
   gap: var(--space-m);
 }
 
-.ap-compose__mode {
-  border: var(--border-width-thin) solid var(--color-outline);
-  border-radius: var(--border-radius-small);
-  display: flex;
-  flex-direction: column;
-  gap: var(--space-s);
-  padding: var(--space-m);
-}
-
-.ap-compose__mode legend {
-  font-weight: 600;
-}
-
-.ap-compose__mode-option {
-  cursor: pointer;
-  display: flex;
-  flex-wrap: wrap;
-  gap: var(--space-xs);
-}
-
-.ap-compose__mode-hint {
-  color: var(--color-on-offset);
-  display: block;
-  font-size: var(--font-size-s);
-  margin-left: 1.5em;
-  width: 100%;
-}
-
 .ap-compose__editor {
   position: relative;
 }
@@ -1027,21 +999,6 @@
   outline-offset: -2px;
 }
 
-.ap-compose__counter {
-  font-size: var(--font-size-s);
-  padding-top: var(--space-xs);
-  text-align: right;
-}
-
-.ap-compose__counter--warn {
-  color: var(--color-yellow50);
-}
-
-.ap-compose__counter--over {
-  color: var(--color-error);
-  font-weight: 600;
-}
-
 .ap-compose__syndication {
   border: var(--border-width-thin) solid var(--color-outline);
   border-radius: var(--border-radius-small);
@@ -2837,11 +2794,6 @@
     box-shadow: 0 2px 8px rgba(255, 255, 255, 0.06);
   }
 
-  /* --- Compose counter warning --- */
-  .ap-compose__counter--warn {
-    color: var(--color-yellow90);
-  }
-
   /* --- Tab badge federated: soften purple --- */
   .ap-tab__badge--federated {
     color: var(--color-purple90);