fix: KEEP-1371 re-apply Next.js 16.1.5 upgrade + world-postgres

[suisuss]

Summary

• Re-applies all changes from PR chore(deps): KEEP-1371 bump next from 16.0.10 to 16.1.5 #229 (reverted in PR Revert "chore(deps): KEEP-1371 bump next from 16.0.10 to 16.1.5" #288 due to CNPG SSL issue on staging)
• Adds CNPG SSL cert analysis doc for the SELF_SIGNED_CERT_IN_CHAIN error

What changed (from original PR #229)

• Next.js 16.0.10 -> 16.1.5
• Workflow SDK switched from Local World to Postgres World
• Full transitive dependency tree for @workflow/world-postgres (standalone tracing + pnpm hoisting)
• Production Helm values updated with postgres world config
• Drizzle schema declares workflow enum types to prevent accidental drops

Known issue: CNPG SSL

Staging crashes on startup with SELF_SIGNED_CERT_IN_CHAIN during world.start() in the instrumentation hook. Analysis and solution options documented in docs/keeperhub/KEEP-1371/CNPG-SSL-WORLD-POSTGRES.md. SSL fix will be added to this PR before merge.

Test plan

• Resolve CNPG SSL cert issue (see doc for options)
• Verify staging app starts and world-postgres initializes
• Verify PR environment still deploys correctly
• Test workflow execution paths 1-4

[suisuss]

@OleksandrUA Please read the doc I added in the last commit, we need to setup the SSL cert and have it accepted by postgres worlds via one of the options