docs: update documentation for Home Assistant integration and Apprise icons

- Add Home Assistant integration guide with REST command examples (README.md)
- Document Apprise `type` field mapping to status icons (✅, ⚠️, ❌) across agent.md and architecture.md
- Update prerequisites to Nextcloud 33 (INSTALL.md)
- Remove outdated link preview suppression note (agent.md)
- Fix folder name casing in troubleshooting section (INSTALL.md)

architecture.md

@@ -201,7 +201,7 @@ In Talk 14+, the `actorDisplayName` field in the Chat API **must match** the bot
 
 ### Sender name embedding
 
-Since NCTalk doesn't support per-message avatars, the app prepends a bold emoji-prefixed sender name line to the message text:
+Since NCTalk doesn't support per-message avatars, the app prepends a type-icon (for Apprise) + emoji-prefixed sender name line to the message text:
 
 ```
 🤖 **CI Bot**
@@ -209,6 +209,16 @@ Since NCTalk doesn't support per-message avatars, the app prepends a bold emoji-
 Build #1234 passed
 ```
 
+For Apprise with a `type` field:
+
+```
+⚠️ 🤖 **CI Bot**
+
+Build #1234 failed
+```
+
+Icons: ✅ (success), ⚠️ (warning), ❌ (error). Info and image types have no icon.
+
 This preserves the visual identity of the sending service within Talk's message rendering.
 
 ### Auth token storage