fix: add missing SEO meta tags to metadata.svelte and news/[slug]

[10-trix]

Description

Fixes missing SEO meta tags on two pages:

1. src/lib/components/metadata.svelte — added og:title, og:description,
   twitter:title, and twitter:description which were absent from the global
   metadata component.

2. src/routes/news/[slug]/+page.svelte — replaced the minimal <svelte:head>
   block (which only had a broken canonical pointing to /news) with a full set
   of SEO meta tags using the blogpost's title, path, and markdown content.

Resolves: #2194

AI Tool Disclosure

• My contribution does not include any AI-generated content
• My contribution includes AI-generated content, as disclosed below:
  • AI Tools: [e.g. GitHub CoPilot, ChatGPT, JetBrains Junie etc.]
  • LLMs and versions: [e.g. GPT-4.1, Claude Haiku 4.5, Gemini 2.5 Pro etc.]
  • Prompts: [Summarize the key prompts or instructions given to the AI tools]

Affirmation

• My code follows the CONTRIBUTING.md guideline

[Adarshkumar0509]

see i have a doubt twitter:title and twitter:description appear twice in the HTML once from the global metadata.svelte and once from the article page. Duplicate meta tags cause unpredictable behavior in search engines and social platforms?