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/memoserv/Cargo.toml

@@ -1,8 +1,8 @@
 [package]
-name = "fedserv-memoserv"
+name = "echo-memoserv"
 version = "0.0.1"
 edition = "2021"
 description = "MemoServ: deliver messages to registered users, online or not."
 
 [dependencies]
-fedserv-api = { path = "../../api" }
+echo-api = { path = "../../api" }

modules/memoserv/src/del.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{Sender, ServiceCtx, Store};
+use echo_api::{Sender, ServiceCtx, Store};
 
 // DEL <num>|ALL: remove a memo (or the whole mailbox).
 pub fn handle(me: &str, from: &Sender, account: &str, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {

modules/memoserv/src/lib.rs

@@ -4,7 +4,7 @@
 //! account data. `lib.rs` holds the dispatcher; each command lives in its own
 //! file, matching NickServ/ChanServ.
 
-use fedserv_api::{NetView, Sender, Service, ServiceCtx, Store};
+use echo_api::{NetView, Sender, Service, ServiceCtx, Store};
 
 #[path = "send.rs"]
 mod send;

modules/memoserv/src/list.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{human_time, Sender, ServiceCtx, Store};
+use echo_api::{human_time, Sender, ServiceCtx, Store};
 
 // LIST: show every memo with a one-line preview; \x02*\x02 marks unread.
 pub fn handle(me: &str, from: &Sender, account: &str, ctx: &mut ServiceCtx, db: &dyn Store) {

modules/memoserv/src/read.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{human_time, MemoView, Sender, ServiceCtx, Store};
+use echo_api::{human_time, MemoView, Sender, ServiceCtx, Store};
 
 // READ <num>|NEW|ALL: display memos and mark them read.
 pub fn handle(me: &str, from: &Sender, account: &str, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {

modules/memoserv/src/send.rs

@@ -1,4 +1,4 @@
-use fedserv_api::{Sender, ServiceCtx, Store};
+use echo_api::{Sender, ServiceCtx, Store};
 
 // A full mailbox rejects new memos, so nobody can be flooded.
 const MAX_MEMOS: usize = 30;