Normalize theme tokens: accent-text, zap-text, remove hard-coded colors

- Add accent-text and zap-text tokens to all 7 themes for proper contrast
  on accent/zap-colored buttons (fixes white-on-light-accent in Catppuccin,
  Nord Frost, Hackerman, Sepia, Gruvbox)
- Replace text-white → text-accent-text on all accent buttons (20+ instances)
- Replace text-white → text-zap-text on zap buttons
- Replace hover:text-white → hover:text-accent-text on follow/action buttons
- Replace bg-blue-500 → bg-accent in FountainCard (theme-aware)
- Remaining text-white is correct: overlays on bg-black, danger badges

src/components/article/ArticleEditor.tsx

@@ -328,7 +328,7 @@ export function ArticleEditor() {
           <button
             onClick={handlePublish}
             disabled={!canPublish || publishing || published}
-            className="px-4 py-1 text-[11px] bg-accent hover:bg-accent-hover text-white transition-colors disabled:opacity-30 disabled:cursor-not-allowed"
+            className="px-4 py-1 text-[11px] bg-accent hover:bg-accent-hover text-accent-text transition-colors disabled:opacity-30 disabled:cursor-not-allowed"
           >
             {published ? "published ✓" : publishing ? "publishing…" : "publish"}
           </button>
@@ -493,7 +493,7 @@ function DraftListView({ onNewDraft }: { onNewDraft: () => void }) {
         </div>
         <button
           onClick={onNewDraft}
-          className="px-3 py-1 text-[11px] bg-accent hover:bg-accent-hover text-white transition-colors"
+          className="px-3 py-1 text-[11px] bg-accent hover:bg-accent-hover text-accent-text transition-colors"
         >
           new draft
         </button>

src/components/article/ArticleFeed.tsx

@@ -68,7 +68,7 @@ export function ArticleFeed() {
         <h1 className="text-text text-sm font-medium">Articles</h1>
         <button
           onClick={() => setView("article-editor")}
-          className="text-[11px] px-3 py-1 border border-accent/60 text-accent hover:bg-accent hover:text-white transition-colors"
+          className="text-[11px] px-3 py-1 border border-accent/60 text-accent hover:bg-accent hover:text-accent-text transition-colors"
         >
           write article
         </button>

src/components/article/ArticleView.tsx

@@ -456,7 +456,7 @@ export function ArticleView() {
                   {loggedIn && (
                     <button
                       onClick={() => setShowZap(true)}
-                      className="text-[11px] px-4 py-1.5 bg-zap hover:bg-zap/90 text-white transition-colors"
+                      className="text-[11px] px-4 py-1.5 bg-zap hover:bg-zap/90 text-zap-text transition-colors"
                     >
                       ⚡ Zap {authorName}
                     </button>