docs, help, checks: the README and the help say what the app does

README: the API table lists every route, twelve of which were missing;
an SFTP section says how to turn the mount on and register a key; the
keys table and the command list cover what was only in the code
(digits, Tab, w, f, Alt-h/l, Ctrl-D/U, m/p, :today, :edit, :next and
the rest, :search!, :set clipboard, :logout!). Three claims that were
wrong are fixed: there is no board button above the list, R does not
rename a space, and Esc/q close the document.

Help gains the agenda keys and the board's gg/G and r. :t no longer
means :today, which read as the agenda's key.

make check runs cargo fmt --check, after the one formatting commit
before this, which .git-blame-ignore-revs names (git config
blame.ignoreRevsFile .git-blame-ignore-revs). Cargo.toml states
rust-version 1.96, the floor the Proton crates set, and the build is
checked on it. make build installs the frontend from the lockfile.

A test reads the route table out of routes/mod.rs and asks every route
without a cookie: all but the login, the health check and the share
links must answer 401, including any route added later.

Cargo.toml

@@ -2,6 +2,8 @@
 name = "narl-workspace"
 version = "0.1.0"
 edition = "2021"
+# The Proton crates set the floor.
+rust-version = "1.96"
 description = "A terminal-themed personal diary for the browser"
 
 [dependencies]