refactor(analytics): centralize landing page Umami tracking via env vars

Replace hardcoded Umami website IDs in all 10 Astro landing pages with
import.meta.env.PUBLIC_UMAMI_WEBSITE_ID, following the same pattern
as the web apps.

- Add UMAMI_WEBSITE_ID_*_LANDING vars for all 10 landings in .env.development
- Add landing page configs to generate-env.mjs
- Replace hardcoded IDs with env var in 7 existing Layout.astro files
- Add Umami tracking to 3 missing landings (NutriPhi, Presi, Mukke)
- Fix Todo Landing invalid ID ("todo-landing" -> proper UUID)
- Update ANALYTICS.md with new landing page IDs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/ANALYTICS.md

@@ -48,6 +48,10 @@ injectUmamiAnalytics(html)    → <script defer src="stats.mana.how/script.js" d
 | Calendar | `84862d98-727e-4e25-8645-639241dd1544` | stats.mana.how/share/calendarlanding |
 | Clock | `0332b471-a022-46af-a726-0f45932bfd58` | stats.mana.how/share/clocklanding |
 | Picture | `d3ac98e6-0d1a-47a3-a218-2a81fff596bd` | stats.mana.how/share/picturelanding |
+| Todo | `538eb4b6-2241-45a3-994d-cdb9bdb0c250` | stats.mana.how/share/todolanding |
+| NutriPhi | `15610d03-b280-4b92-9c71-0ef89c23202b` | stats.mana.how/share/nutriphilanding |
+| Presi | `dd485016-0077-47b9-9f59-ab2c6c1730ee` | stats.mana.how/share/presilanding |
+| Mukke | `b2c9ab34-3c53-4463-9dde-1ecf098886a5` | stats.mana.how/share/mukkelanding |
 
 ### Web Apps