Add multiplayer bots, typing languages, and rework the UI layout

Multiplayer
- Quick match: POST /api/multiplayer/quickmatch returns whichever room is
  still filling, or opens one. Players never see a room code; joining by
  code stays for racing specific people.
- Bots fill quick-match rooms after a short wait so a new game is never an
  empty lobby. They only ever join quick-match rooms, never a room opened
  by code. One or two per room, drawn from separate ~40 and ~80 WPM tiers so
  two bots are never near each other's pace, and they stall to correct
  mistakes rather than typing a clean straight line.
- Live player count via GET /api/multiplayer/online, shown on the
  Multiplayer control and under the main menu's Multiplayer button.
- Per-racer colours: you are the theme accent, opponents take distinct hues
  that stay the same from lobby to race.
- The countdown no longer holds the room lock for its full three seconds,
  which is what reset clients mid-countdown.

Typing languages
- 16 languages for the generated-word modes, each with its own
  high-frequency vocabulary rather than a translation of the English list.
- Picker in the top-right rail; non-English uses its own list at every
  difficulty tier instead of falling back to English words.

Fix UTF-8 accuracy in the game core
- update_game_state mixed byte and character counts: total_characters_typed
  accumulated byte-length deltas while total_correct_characters compared a
  char index against that byte count. Equal on ASCII, so it went unnoticed;
  a correctly typed Spanish passage scored 6%. The old byte slicing would
  also have panicked if an index landed inside a multi-byte character.
  Rewritten char-based, with regression tests.

Programming mode
- Replaced prose about programming with real code: 26 syntax-highlighted
  snippets across JavaScript, Python, Rust, C/Go/Java and shell. Single-line
  by necessity, since the typing input is a single-line field.

Layout and readability
- One icon rail arrangement on every screen: Settings/Store under the
  wordmark, Language/Theme/Friends/Account top-right, Stats/Leaderboard/
  Multiplayer bottom-right.
- Main menu: mode picker moved out of the Single Player button, which it was
  notching a divider through and pushing the label off-centre.
- Escape returns to the menu, closing any open popover first, and confirms
  before abandoning a live race.
- Split --text-color and --sub-color per theme; they shared one value that
  measured 3.65:1 against the background, below the 4.5:1 body-text floor.
- Semantic colours used in exactly one place each: gold for a personal best,
  amber for the race countdown and the mobile-result badge.
- Passage now sits in the same place on the typing and end screens, and its
  column is a whole number of characters wide so wrapping cannot leave a
  permanent gap on the right.
- End screen: keystrokes and a correct/wrong/extra/missed split, attribution
  carried over from the typing screen, and a graph with a separate error
  axis, axis titles including seconds, and smoothed lines.

1 files changed, 17 insertions, 0 deletions

diff --git a/data/packs/movies.json b/data/packs/movies.json
new file mode 100644
index 0000000..bc56cad
--- /dev/null
+++ b/data/packs/movies.json
@@ -0,0 +1,17 @@
+[
+  {"category":"movies","content":"The first feature length narrative film, The Story of the Kelly Gang, was made in Australia in 1906 and ran for about an hour.","attribution":"Film"},
+  {"category":"movies","content":"The Wizard of Oz was one of the first major films to use Technicolor extensively, transitioning from black and white to vivid color once Dorothy arrives in Oz.","attribution":"Film"},
+  {"category":"movies","content":"Alfred Hitchcock was known for making brief cameo appearances in nearly all of his own films, a habit that became something of a signature.","attribution":"Film"},
+  {"category":"movies","content":"The special effects in the original Star Wars trilogy were largely achieved with physical models and practical effects, long before computer generated imagery became common.","attribution":"Film"},
+  {"category":"movies","content":"Citizen Kane, released in 1941, is frequently cited by critics and filmmakers as one of the greatest films ever made, praised for its innovative camera work and narrative structure.","attribution":"Film"},
+  {"category":"movies","content":"The word cinema comes from the Greek word for movement, reflecting how early filmmakers were fascinated by the illusion of motion created by a sequence of still images.","attribution":"Film"},
+  {"category":"movies","content":"Pixar's first feature film, Toy Story, released in 1995, was the first full length movie created entirely with computer animation.","attribution":"Film"},
+  {"category":"movies","content":"The Academy Awards, commonly known as the Oscars, have been presented annually since 1929 to honor achievements in the film industry.","attribution":"Film"},
+  {"category":"movies","content":"Silent films relied on live musicians and title cards to convey dialogue and emotion, since synchronized sound was not introduced into feature films until the late 1920s.","attribution":"Film"},
+  {"category":"movies","content":"A film's score is often composed after the movie has been edited, allowing the composer to match the music precisely to the pacing and mood of each scene.","attribution":"Film"},
+  {"category":"movies","content":"The highest grossing films of all time are dominated by franchises built around superheroes, fantasy worlds, and long running science fiction universes.","attribution":"Film"},
+  {"category":"movies","content":"Stop motion animation creates the illusion of movement by photographing physical objects one frame at a time and repositioning them slightly between each shot.","attribution":"Film"},
+  {"category":"movies","content":"The Cannes Film Festival, held annually in France since 1946, is considered one of the most prestigious film festivals in the world.","attribution":"Film"},
+  {"category":"movies","content":"Method acting, popularized in the mid twentieth century, encourages performers to draw on personal memories and emotions to portray a character as realistically as possible.","attribution":"Film"},
+  {"category":"movies","content":"A film's runtime is typically decided during editing, where an editor works with hours of raw footage to shape a coherent story within a manageable length.","attribution":"Film"}
+]