fix: Increase scrollback buffer height for chat rendering (PAD_SIZE)

f27fa98 commit introduced issue of scrolling seemingly randomly being stuck and the following message flood in the logs: "WRN: Ncurses Overflow..."

A pad is an off-screen buffer — larger than the visible terminal screen — that you can scroll, render parts of, or update selectively.

Unlike regular windows, a pad is not tied to screen size. You can create a pad that's 1,000 lines tall, even if your terminal is only 40 lines tall.

This commit addresses the issue by increasing PAD_SIZE to a reasonable number,
allowing messages from buffer to be displayed without overflowing NCurses' window size (maxy).

Minor change: add .cache folder to gitignore

.gitignore

@@ -44,6 +44,9 @@ src/gitversion.h.in
 src/stamp-h1
 src/plugins/profapi.lo
 
+# clangd
+.cache/
+
 # out-of-tree build folders
 build*/