flare: add patched flare-signal with five local feature patches

- patches/flare/000{1..5}-*.patch: typing indicators, formatted
  messages, edited messages, multi-select with delete-for-me, and
  in-channel message search. Mirror the matching commits in
  ~/projects/forks/flare and apply cleanly on top of upstream 0.20.4
  (which is what nixpkgs ships).
- home/profiles/gui.nix: include a flare-signal override that appends
  the patches via overrideAttrs. None of them touch Cargo.lock so the
  cargoDeps hash stays valid; signal-desktop stays alongside it.

home/profiles/gui.nix

@@ -86,6 +86,21 @@
 
         signal-desktop
 
+        # alternative GTK signal client; carries five local feature patches
+        # under patches/flare/ on top of upstream 0.20.4 (typing indicators,
+        # formatted messages, edited messages, multi-select with delete-for-me,
+        # and in-channel message search).
+        (pkgs.flare-signal.overrideAttrs (old: {
+          patches = (old.patches or [ ]) ++ [
+            ../../patches/flare/0001-feat-typing-Implement-typing-indicators.patch
+            ../../patches/flare/0002-feat-messages-Implement-formatted-messages.patch
+            ../../patches/flare/0003-feat-messages-Implement-edited-messages.patch
+            ../../patches/flare/0004-feat-messages-Multi-select-messages-and-delete-for-m.patch
+            ../../patches/flare/0005-feat-messages-In-channel-message-search.patch
+            ../../patches/flare/0006-feat-messages-Show-This-message-was-deleted.-placeho.patch
+          ];
+        }))
+
         # accounting
         # gnucash