feat: improve SEO with locale-specific metadata, structured data, and keywords

- Add locale-specific title/description for DE and EN homepage
- Expand keywords with local SEO terms (Webentwicklung Osnabrück, Informatik, etc.)
- Add WebSite schema and enhance Person schema with knowsAbout, alternateName
- Add hreflang alternates for DE/EN
- Update projects page with locale-specific metadata
- Keep visible titles short, move SEO terms to description/structured data

messages/de.json

@@ -34,7 +34,7 @@
         "f2": "Docker Swarm & CI/CD",
         "f3": "Self-Hosted Infrastruktur"
       },
-      "description": "Ich bin Dennis, Student aus Osnabrück und leidenschaftlicher Selfhoster. Ich entwickle Fullstack Apps und sorge am liebsten selbst dafür, dass sie auf meiner eigenen Infrastruktur perfekt laufen.",
+      "description": "Ich bin Dennis Konkol, Informatik-Student und Webentwickler aus Osnabrück. Ich entwickle Fullstack-Apps mit Next.js und Flutter und betreibe meine eigene Infrastruktur mit Docker und CI/CD.",
       "ctaWork": "Meine Projekte",
       "ctaContact": "Kontakt"
     },

messages/en.json

@@ -35,7 +35,7 @@
         "f2": "Docker Swarm & CI/CD",
         "f3": "Self-Hosted Infrastructure"
       },
-      "description": "I'm Dennis, a student from Germany and a passionate selfhoster. I build fullstack applications and love the challenge of managing the infrastructure they run on.",
+      "description": "I'm Dennis Konkol, a computer science student and web developer from Osnabrück, Germany. I build fullstack apps with Next.js and Flutter and love running my own infrastructure with Docker and CI/CD.",
       "ctaWork": "View Projects",
       "ctaContact": "Get in touch"
     },