docs: fix incorrect claims, add missing tools, and release guide

[vredchenko]

Summary

PR 1 of the documentation audit (#187). Fixes factually incorrect content, fills completeness gaps, and adds a release procedure guide.

• Fix ARIA definition in glossary — was incorrectly described as an image analysis system; now correctly describes it as a central metadata repository
• Fix phantom tools in api-server.md — replaced nonexistent simulate_msg module and simulate-messages.sh with actual external_message_simulator.py; clarified dev-k8s.sh lives in smartem-devtools
• Rewrite generate-docs.md — replaced stale tox -e docs reference with actual MDX sync + webui workflow
• Fix database.md — enumerate all 6 migrations (was 3 + vague "apply remaining"); replace stale revision ID 6e6302f1ccb6 with actual migration filename
• Add 4 undocumented tools to tools.md: check_schema_drift.py, db_table_totals.py, generate_api_docs.py, makeiso.sh
• Add release procedure guide (docs/operations/releasing.md) covering smartem-decisions, smartem-epuplayer, and smartem-workspace — tag conventions, versioning, artifacts, manual releases, verification, uvx cache gotcha
• Update operations index — link releasing and PyPI setup docs in toctree + Topics

Test plan

• cd webui && npm run build passes — all docs sync and compile without errors
• Visually check affected pages render correctly in dev server
• Verify internal cross-links resolve (glossary, tools reference from api-server, releasing <-> pypi-publish)

Ref: #187