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, 19 insertions, 0 deletions

diff --git a/data/packs/quotes.json b/data/packs/quotes.json
new file mode 100644
index 0000000..c727b81
--- /dev/null
+++ b/data/packs/quotes.json
@@ -0,0 +1,19 @@
+[
+  {"category":"quotes","content":"The only limit to our realization of tomorrow is our doubts of today.","attribution":"Franklin D. Roosevelt"},
+  {"category":"quotes","content":"It always seems impossible until it's done.","attribution":"Nelson Mandela"},
+  {"category":"quotes","content":"Stay hungry, stay foolish.","attribution":"Steve Jobs"},
+  {"category":"quotes","content":"Four score and seven years ago our fathers brought forth on this continent a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.","attribution":"Abraham Lincoln, The Gettysburg Address"},
+  {"category":"quotes","content":"You have power over your mind, not outside events. Realize this, and you will find strength.","attribution":"Marcus Aurelius, Meditations"},
+  {"category":"quotes","content":"I went to the woods because I wished to live deliberately, to front only the essential facts of life, and see if I could not learn what it had to teach, and not, when I came to die, discover that I had not lived.","attribution":"Henry David Thoreau, Walden"},
+  {"category":"quotes","content":"It is not the critic who counts; not the man who points out how the strong man stumbles. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood.","attribution":"Theodore Roosevelt, Citizenship in a Republic"},
+  {"category":"quotes","content":"If there is no struggle, there is no progress. Those who profess to favor freedom, and yet depreciate agitation, are men who want crops without plowing up the ground.","attribution":"Frederick Douglass"},
+  {"category":"quotes","content":"The two most important days in your life are the day you are born and the day you find out why.","attribution":"Mark Twain"},
+  {"category":"quotes","content":"To be great is to be misunderstood.","attribution":"Ralph Waldo Emerson, Self-Reliance"},
+  {"category":"quotes","content":"Whatever you are, be a good one.","attribution":"Abraham Lincoln"},
+  {"category":"quotes","content":"If I have seen further, it is by standing on the shoulders of giants.","attribution":"Isaac Newton"},
+  {"category":"quotes","content":"Genius is one percent inspiration and ninety-nine percent perspiration.","attribution":"Thomas Edison"},
+  {"category":"quotes","content":"That man over there says that women need to be helped into carriages, and lifted over ditches, and to have the best place everywhere. Nobody ever helps me into carriages, or over mud puddles, or gives me any best place, and ain't I a woman?","attribution":"Sojourner Truth, Ain't I a Woman?"},
+  {"category":"quotes","content":"Failure is impossible.","attribution":"Susan B. Anthony"},
+  {"category":"quotes","content":"Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome while trying to succeed.","attribution":"Booker T. Washington"},
+  {"category":"quotes","content":"Our greatest glory is not in never falling, but in rising every time we fall.","attribution":"Confucius"}
+]