/clear_cache with no argument wipes the whole link_cache table;
with a post URL it removes that single entry (normalized via
site::cache_key so fxtwitter/mobile/photo variants collide with
the write-side key). Non-admins get 'Admin only.'. LinkCache gains
clear(Option<&str>) -> usize reporting removed rows.
Converge the duplicated open_db (open + busy_timeout) and the
spawn_blocking + expect ceremony that every table access repeated
into one db.rs module. ChatStore no longer creates the tasks table
(schema ownership: queue.rs owns tasks, state.rs chat_state,
link_cache.rs link_cache). No schema or behavior change - all
CREATE TABLE statements are byte-identical, IF NOT EXISTS stays
idempotent, so existing data/task_queue.db files need no migration.
All bot commands now carry English descriptions, shown in the Telegram
command menu and by /help (which prints Command::descriptions()). The
README command table explains each command's arguments and behavior:
forward channel (@channel or ID), edit-before-forward flow, template
[] placeholder semantics and per-site caption format placeholders.