style: format the whole tree with cargo fmt (stock defaults, #35)

One-time, mechanical reformat — no functional changes. The tree was not
rustfmt-clean (~1800 hunks across ~100 files); this brings it to stock
`cargo fmt` defaults so a `cargo fmt --check` CI gate can follow.
Behaviour-preserving: 2509 pass / 0 fail / 1 ignored (unchanged baseline),
clippy clean. A .git-blame-ignore-revs entry follows so `git blame`
skips this commit.

src/event.rs

@@ -8,9 +8,8 @@
 use crossterm::event::KeyEvent;
 
 use crate::db::{
-    AddColumnResult, ChangeColumnTypeResult, DataResult, DbError, DeleteResult,
-    DropColumnResult, InsertResult, QueryPlan, RelationshipDiagramData, TableDescription,
-    UpdateResult,
+    AddColumnResult, ChangeColumnTypeResult, DataResult, DbError, DeleteResult, DropColumnResult,
+    InsertResult, QueryPlan, RelationshipDiagramData, TableDescription, UpdateResult,
 };
 use crate::dsl::Command;
 
@@ -73,10 +72,16 @@ pub enum AppEvent {
     },
     /// An `explain …` command succeeded (ADR-0028). `plan`
     /// carries the captured query plan; nothing was executed.
-    DslExplainSucceeded { command: Command, plan: QueryPlan },
+    DslExplainSucceeded {
+        command: Command,
+        plan: QueryPlan,
+    },
     /// A `show <kind>` list command (V5) — carries pre-formatted
     /// display lines (tables / relationships / indexes).
-    DslShowListSucceeded { command: Command, lines: Vec<String> },
+    DslShowListSucceeded {
+        command: Command,
+        lines: Vec<String>,
+    },
     /// `show relationship <name>` (ADR-0044) — structured data for the
     /// diagram, rendered App-side; `None` when no such relationship.
     DslShowRelationshipSucceeded {