docs: improve SEO for homepage title and description

[ekline]

Context

This PR addresses an SEO issue identified by auditing the documentation (130 pages) against Okteto's keyword strategy derived from the marketing website.

Keyword map

Primary keywords identified from okteto.com:

• cloud development environment / cloud development environments
• Kubernetes development environment
• development platform
• Okteto Platform, Okteto CLI, Okteto Manifest
• preview environments, remote development

Secondary keywords:

• inner loop development, development velocity, platform engineering
• developer self-service, golden paths, live updates

Audience terms: platform engineers, platform teams, developers

Top 3 findings

Rank	Priority	Page	Issue	Proposed fix
1	High	src/content/index.md	Homepage title "Welcome to Okteto!" (18 chars) contains zero target keywords. Description is 76 chars — under the 120-160 sweet spot.	Fixed in this PR — Title → Okteto docs - cloud development environments for Kubernetes (60 chars). Description expanded to 149 chars with keywords.
2	High	src/content/self-hosted/install/certificates/cert-manager.mdx	Truncated title: "Setting up certificates with" — missing the subject (cert-manager).	Follow-up
3	Medium	src/content/reference/index.mdx	Title is only "References" (10 chars), no description field. Key navigation page.	Follow-up

What this PR fixes

The docs homepage (src/content/index.md) is the single most important page for search rankings. The title "Welcome to Okteto!" and short description contained none of Okteto's target keywords.

Changes (frontmatter only — no content changes):

• Title: Welcome to Okteto! → Okteto docs - cloud development environments for Kubernetes (60 chars, includes two primary keywords)
• Description: Expanded from 76 to 149 chars, now includes "cloud development environments", "Kubernetes", and action-oriented language

Remaining items

• Fix truncated title on cert-manager.mdx ("Setting up certificates with" — incomplete)
• Add title and description to reference/index.mdx
• 8 pages missing descriptions entirely
• 27 pages with titles under 30 characters
• 3 sets of duplicate titles (GitHub, Volume Snapshots, Registry Credentials)
• ~85 pages where titles lack keyword alignment

Audit summary

Metric	Count
Pages scanned	130
Pages missing descriptions	8
Duplicate title sets	3 (6 pages)
Titles under 30 chars	27
Descriptions under 120 chars	30
Title keyword alignment gaps	~85

How to verify

1. Check that the updated frontmatter renders correctly: npm start and visit the docs homepage
2. Confirm the page title and meta description appear correctly in the browser tab and page source

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