feat(seo): make linkedin required for blog authors

[vfanucci]

Summary

Completes the work started in #4469 by ensuring every blog post has the linkedin field and making it required in the Zod schema so future posts fail at build time without it.

• 15 posts backfilled with real LinkedIn URLs (Shruti Mantri, Elliot Gunn, Federico Trotta, Parham Parvizi, Ludovic Dehon, Emmanuel Darras)
• 10 posts backfilled with empty string "" (external contributors: Dario Radecic, Kevin Fleming, Anuun Chinbat, Julien Legrand — LinkedIn URLs unconfirmed)
• content.config.ts: linkedin changed from z.string().optional() to z.string() in both author and authors schemas

Why this matters

Without this change, new blog posts can be published without a linkedin field, which means the JSON-LD author.sameAs property (added in #4469) would silently be missing. Making it required ensures:

• Every future post must declare the field
• Build fails immediately if forgotten
• Empty string "" is valid for external authors (the Astro template already handles falsy values gracefully)

Test plan

• Changes verified in dev/preprod
• No unrelated files modified
• YAML validated (for blueprint PRs)
• astro sync passes with no content collection errors
• Verify JSON-LD output includes sameAs for posts with real URLs
• Verify JSON-LD output omits sameAs for posts with linkedin: ""

🤖 Generated with Claude Code

[github-actions]

☁️ Cloudflare Worker Preview Deployed!

🔗 https://ks-seo-blog-author-linkedin-requi-docs.kestra-io.workers.dev
🔗 https://fa85fbe8-docs.kestra-io.workers.dev

## 🔦 Lighthouse Benchmark

Tested: https://ks-seo-blog-author-linkedin-requi-docs.kestra-io.workers.dev on 2026-04-14 14:13 UTC
Compared against main baseline from 2026-04-10

Scores (0–100, higher is better)

Page	Performance	Accessibility	Best Practices	SEO
Home	62	79	59	92
Pricing	98	88	59	100
Enterprise	91	78	59	100
Cloud	90	83	59	100
About Us	99	87	59	100
Docs Landing	93	84	59	92
Contribute to Kestra (simple docs)	98	84	59	92
Flow (full featured docs)	94	86	59	92
Blog Index	65 🔻 -16	86	59	100
Blog Post (sample)	88	83	59	100
VS Page (sample)	97	88	59	100
Plugins Landing	93	77	59	92
Plugin Page (sample)	96	87	59	100
Plugin Debug Page (sample)	96	87	59	100
Plugin Debug Return Page (sample)	96	87	59	100
Blueprints Landing	91	77	56	92
Blueprint Audit Logs CSV Export	70	82	59	100

Core Web Vitals (lower is better)

Page	LCP	FCP	TBT	CLS	Speed Index
Home	1.87 s 🟢	1.13 s 🟢	458 ms 🔻	0.002	3.18 s 🟢
Pricing	1.00 s	0.57 s	52 ms	0.000	0.85 s
Enterprise	1.88 s	0.88 s	55 ms 🔻	0.003	1.03 s 🟢
Cloud	2.09 s	0.54 s	47 ms 🔻	0.000	1.01 s
About Us	0.99 s	0.54 s	49 ms 🟢	0.000	0.87 s
Docs Landing	1.14 s	0.47 s 🟢	167 ms	0.000	1.08 s
Contribute to Kestra (simple docs)	0.97 s	0.50 s 🟢	100 ms 🔻	0.000	0.66 s 🟢
Flow (full featured docs)	0.85 s 🟢	0.56 s 🟢	174 ms	0.000	1.07 s
Blog Index	7.61 s 🔻	0.61 s	58 ms	0.000	22.64 s 🔻
Blog Post (sample)	2.36 s 🔻	0.46 s 🟢	53 ms 🔻	0.000	0.67 s 🟢
VS Page (sample)	1.21 s	0.57 s	58 ms	0.000	0.86 s
Plugins Landing	0.96 s 🟢	0.53 s	78 ms 🔻	0.000	2.51 s 🔻
Plugin Page (sample)	0.96 s	0.47 s	24 ms	0.000 🟢	1.78 s
Plugin Debug Page (sample)	0.96 s	0.54 s	77 ms	0.001	1.80 s 🔻
Plugin Debug Return Page (sample)	0.85 s 🟢	0.45 s	89 ms	0.025	1.71 s
Blueprints Landing	1.40 s	0.82 s	61 ms	0.001	2.04 s 🔻
Blueprint Audit Logs CSV Export	0.91 s 🟢	0.60 s	145 ms	0.485	2.27 s

Legend

🟢 improved  ·  🔻 regressed  ·  (blank) no significant change
Score threshold: ±10 pts  ·  Metric threshold: ±30% of baseline