[fix](trx-server): include legacy home config path and coords in print-config

Fix server config discovery to include ~/.trx-server.toml and update
example/print-config output to explicitly include general latitude and
longitude fields.

Also update config docs and add a test for the legacy search path.

Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

trx-server.toml.example

@@ -2,6 +2,7 @@
 #
 # Copy this file to one of:
 #   ./trx-server.toml                   (current directory)
+#   ~/.trx-server.toml                  (legacy user config)
 #   ~/.config/trx-rs/server.toml        (user config)
 #   /etc/trx-rs/server.toml             (system-wide)
 #