Rename the project to Echo (was fedserv)

Rebrand the daemon and workspace: the binary is now `echo`, every crate
is `echo-*` (`echo-api` and the module crates), Rust imports use
`echo_*`, the gRPC proto is `proto/echo.proto` with package `echo.v1`,
and the log filter, gossip peer-name default, and on-disk store default
(`echo.db.jsonl`) follow. Docs updated throughout. No behaviour change;
crate directories and the config schema are untouched.

modules/infoserv/src/del.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{Priv, Sender, ServiceCtx, Store};
+use echo_api::{Priv, Sender, ServiceCtx, Store};
 
 // DEL/ODEL <number>: remove a bulletin by its listed position. Admin only.
 pub fn handle(me: &str, from: &Sender, kind: &str, num: Option<&str>, ctx: &mut ServiceCtx, db: &mut dyn Store) {

modules/infoserv/src/lib.rs

@@ -9,7 +9,7 @@
 //! and any operator may OLIST. `lib.rs` holds the dispatcher; each command
 //! (parameterised by bulletin kind) lives in its own file.
 
-use fedserv_api::{NetView, Sender, Service, ServiceCtx, Store};
+use echo_api::{NetView, Sender, Service, ServiceCtx, Store};
 
 #[path = "post.rs"]
 mod post;

modules/infoserv/src/list.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{Sender, ServiceCtx, Store};
+use echo_api::{Sender, ServiceCtx, Store};
 
 // LIST/OLIST: show the bulletins of a kind. Public is open; oper is oper-only.
 pub fn handle(me: &str, from: &Sender, kind: &str, oper_only: bool, ctx: &mut ServiceCtx, db: &mut dyn Store) {

modules/infoserv/src/post.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{Priv, Sender, ServiceCtx, Store};
+use echo_api::{Priv, Sender, ServiceCtx, Store};
 
 // POST/OPOST <message>: add a bulletin (public or oper). Admin only.
 pub fn handle(me: &str, from: &Sender, kind: &str, rest: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {