docs: move SolidStart v1 docs under /v1

[birkskyum]

• I have read the Contribution guide

• This PR references an issue (except for typos, broken links, or other minor problems)

• Closes Start-specific labels ( v1 and v2 ) #1590

Description(required)

Moves the SolidStart v1 documentation from the unversioned /solid-start/ route to /solid-start/v1/.

• Registers v1 and v2 as the available SolidStart documentation versions and gives v1 its own filesystem sidebar.
• Lists SolidStart v2 before v1 in the version selector.
• Updates v1 cross-references and other Solid docs links to target an explicit SolidStart version.
• Redirects the bare /solid-start route to v2 while permanently redirecting legacy unversioned page URLs to their v1 equivalents.
• Enables the existing legacy-route middleware and keeps the redirect-only /solid-start path out of static prerender output.
• Marks the SST deployment guide as SolidStart v1-only, directs v2 readers to the deployment-plugin guide, and refreshes the v1 AWS Lambda streaming configuration.
• Bumps SolidBase to 0.6.13 and uses its contextual route metadata to label SolidStart v1 as v1 (legacy) without changing other projects' version labels.
• Updates the custom version selector to consume SolidBase's route-aware options hook so contextual labels are rendered.

Verification

• pnpm check:types
• pnpm check:lint
• pnpm build (271 routes prerendered)
• Interactive version-selector checks for SolidStart v1/v2 and Solid Meta
• HTTP checks for v1/v2 pages and legacy 301 redirects

Related issues & labels

• Suggested label(s) (optional): documentation

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