ci: add GitHub Actions workflows with semantic-release auto-versioning

chore: fix all 702 clippy warnings across codebase
- auto-fix 475 via cargo clippy --fix
- fix remaining 227 manually: uninlined_format_args, redundant_closure, match_same_arms,
  underscore_binding, format_push_string, items_after_statements, needless_pass_by_value,
  clone_on_copy, case_sensitive_extension, single_match/let-else, write_with_newline,
  and other clippy lints

src/model/msglog/schema.rs

@@ -1,4 +1,4 @@
-//! SQLite schema definition for the message log database.
+//! `SQLite` schema definition for the message log database.
 
 use rusqlite::Connection;
 use anyhow::Result;
@@ -9,7 +9,7 @@ use anyhow::Result;
 /// Why: idempotent via `CREATE TABLE/INDEX IF NOT EXISTS`, so it's safe
 /// to call on every `open_or_create`.
 ///
-/// Return: `Ok(())` on success, or the underlying SQLite error.
+/// Return: `Ok(())` on success, or the underlying `SQLite` error.
 pub fn init_schema(conn: &Connection) -> Result<()> {
     conn.execute_batch("PRAGMA foreign_keys = ON;")?;
     conn.execute_batch(