feat: expand to 1014 words, add title-case display and 2 new themes

- Move word data from hardcoded seed.py to data/words.json
- Expand from 210 words across 7 categories to 1014 words across 14
  categories (animals, food, colors, sports, space, nature, music,
  science, countries, occupations, ocean, weather, mythology, technology)
- Word list sidebar now shows title case (Tiger) while grid stays
  uppercase; text input remains case-insensitive
- Add Ocean theme (light, blue accents) and Forest theme (dark, amber
  accents on deep green)
- Replace hardcoded rgba values with --coral-bg CSS variable so
  selection highlighting adapts per theme

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

static/js/theme.js

@@ -0,0 +1,34 @@
+(function () {
+    "use strict";
+
+    var themes = ["indigo", "dark", "light", "ocean", "forest"];
+    var icons = {
+        indigo: "bi-moon-stars",
+        dark: "bi-circle-half",
+        light: "bi-sun",
+        ocean: "bi-water",
+        forest: "bi-tree"
+    };
+    var lightThemes = { light: true, ocean: true };
+    var btn = document.getElementById("theme-toggle");
+    var current = localStorage.getItem("ws-theme") || "indigo";
+
+    function apply(theme) {
+        document.documentElement.setAttribute("data-theme", theme);
+        document.documentElement.setAttribute(
+            "data-bs-theme",
+            lightThemes[theme] ? "light" : "dark"
+        );
+        btn.querySelector("i").className = "bi " + icons[theme];
+        btn.title = theme.charAt(0).toUpperCase() + theme.slice(1) + " theme";
+        localStorage.setItem("ws-theme", theme);
+        current = theme;
+    }
+
+    apply(current);
+
+    btn.addEventListener("click", function () {
+        var idx = (themes.indexOf(current) + 1) % themes.length;
+        apply(themes[idx]);
+    });
+})();