Some small Labrinth refactors and fixes (#3698)

* chore(labrinth): fix typos, simplify out `remove_duplicates` func

* fix(labrinth): implement `capitalize_first` so that it can't panic on wide chars

* chore(labrinth): refactor out unneeded clone highlighted by nightly Clippy lints

* chore(labrinth): simplify `capitalize_first` implementation

* fix(labrinth): preserve ordering when deduplicating project field values

This addresses an unintended behavior change on
157647faf2778c74096e624aeef9cdb79539489c.

* fix(labrinth/tests): make `index_swaps` test run successfully

I wonder why we don't run these more often...

* refactor: rename `.env.example` files to `.env.local`, make local envs more consistent between frontend and backend

* chore(labrinth/.env.local): proper email verif. and password reset paths

apps/labrinth/src/routes/v2_reroute.rs

@@ -264,11 +264,11 @@ pub fn convert_side_types_v2_bools(
 }
 
 pub fn capitalize_first(input: &str) -> String {
-    let mut result = input.to_owned();
-    if let Some(first_char) = result.get_mut(0..1) {
-        first_char.make_ascii_uppercase();
-    }
-    result
+    input
+        .chars()
+        .enumerate()
+        .map(|(i, c)| if i == 0 { c.to_ascii_uppercase() } else { c })
+        .collect()
 }
 
 #[cfg(test)]