Add WhisperTyping feature parity #4033

Originally written by @ccantynz-alt on GitHub.
Imported from https://github.com/ccantynz-alt/48co.v1/pull/4

Summary\n\nBrings 48co to feature parity with WhisperTyping — a paid Windows desktop voice dictation app — but free and in the browser.\n\n- 50+ language support — Language selector in popup, wired through to both Web Speech API and Whisper API engines\n- Voice punctuation & emoji — Say "period", "comma", "new line", "question mark", "thumbs up emoji" etc. and they're inserted as symbols\n- Smart post-processing — Auto-capitalizes sentences, cleans up spacing around punctuation, formats text naturally\n- Push-to-talk mode — Hold Ctrl+Shift to record, release to stop (configurable toggle in settings)\n- Custom vocabulary — Add technical terms, brand names, jargon with custom word replacements\n- Text replacement rules — Configurable find-and-replace patterns for abbreviations and corrections\n- Any-website support — Extension now runs on ALL websites, not just 4 AI chat sites. Generic adapter finds focused text inputs automatically\n- Updated landing page — New features grid, WhisperTyping in comparison table, updated hero copy\n- Updated welcome page — Reflects all new capabilities and activation modes\n\n## Test plan\n\n- [ ] Load extension in Chrome, verify widget appears on AI chat sites (Claude, ChatGPT, Gemini, DeepSeek)\n- [ ] Verify widget also appears on non-AI sites (Gmail, Google Docs, etc.)\n- [ ] Test language selector in popup — change language and verify Web Speech recognition uses it\n- [ ] Test voice punctuation: say "hello period how are you question mark" and verify output\n- [ ] Test push-to-talk: enable in settings, hold Ctrl+Shift, speak, release\n- [ ] Test custom vocabulary: add a term in popup, verify it's replaced in transcription\n- [ ] Test text replacements: add a rule, verify find-and-replace works\n- [ ] Verify landing page builds and displays correctly with new features\n- [ ] Verify welcome page shows updated content\n\nhttps://claude.ai/code/session_01Evp2fry1Yo49UD5HGMoi8x