docs(cloud): Final rollout cleanup (paragraph-start inline-code + intro cross-links)

[developerjamiu]

Final cleanup PR for the Cloud IA rollout (issue #568), stacked on #627 (PR 14). Two commits.

Commit 1: paragraph-start inline-code fixes

The recurring house-style §6 violation (inline code at the start of a sentence or paragraph). Caught via sweep, fixed across four pages:

• concepts/database.md: "The scloud db wipe command deletes..."
• concepts/deployments.md: "The scloud CLI may generate..."
• concepts/passwords-secrets-env-vars.md: "Run scloud password list to see them grouped..."
• guides/ship-non-dart-files.md: "The assets/ name is the Serverpod naming convention..."

Commit 2: intro cross-links (per Alex's note)

The capability bullets in the introduction's "What Serverpod Cloud manages" section now link to their corresponding concept or guide pages, so a reader who hits Managed Postgres / Secrets / Custom domains / Logs / PubSub can jump straight to the relevant page. Two bullets (Runtime and scaling, Networking and TLS) don't have a clean 1:1 destination and stay unlinked.

Out of scope

• Sidebar collapse state: surveyed and confirmed the existing arrangement is the right balance (learning sections open, lookup section closed). No change.
• Plans-and-pricing follow-up from issue cloud: Implement the new IA #568: already addressed in cloud_docs/getting-started/launch.md:30 (link to serverpod.dev/cloud exists). Marked resolved on the issue comment.

Test plan

• npm run build passes
• Open the four touched pages and verify the sentences read naturally
• Open the introduction and click each linked bullet topic; confirm they land on the right concept / guide

[Swiftaxe]

LGTM!