docs: make Aspire composition and external Prisma adapters pasteable

[rickylabs]

Summary

• replace the flagship composeAppHost sample with a complete production-shaped plugin contribution and host composition
• document focused application imports, the supported public aggregate, and schema/editor generation
• add an app-local Prisma libSQL/Turso path with explicit ownership boundaries and decision rules; dependency pinning and an exact emitted-sample type-check remain for docs(database): teach arbitrary Prisma driver adapters with a libSQL/Turso example #1101

Refs #1101
Closes #1107

Validation

• deno test --allow-all packages/aspire/tests/ — 19 tests / 68 steps passed
• scoped Aspire check — 45 files, zero errors
• root scoped check — 2,541 files / 22 batches, zero errors
• root lint/fmt wrappers — zero findings
• deno task --cwd docs/site verify — 590 files; 29,669 links across 213 pages resolve; caveats valid
• deno.lock unchanged; no AppHost, Docker, or external service started

Acceptance evidence

The focused fixture compiles and executes the same production entrypoints and composition shape shown in the flagship example. The database guidance accurately describes ownership and operational constraints, but the exact sample does not yet prove installation/pinning of @prisma/adapter-libsql or type-check against a freshly generated client. Those unmet close gates remain tracked by #1101 in 0.0.5.

[rickylabs]

Independent acceptance review closes #1107 only: its six criteria are proven by the complete production-shaped composeAppHost example, focused/public entrypoint guidance, schema generation workflow, executable Aspire fixture, and focused tests/import checks. I refused #1101 criteria 1 and 5: the libSQL sample omits the required @prisma/adapter-libsql add/pin step and the exact sample was not generated/type-checked against a fresh Prisma Deno client. The PR now uses Refs #1101; that issue moved to 0.0.5 with both boxes left unchecked. Its three genuinely supported ownership/decision criteria were checked.