add APEX administration skills

[ORAsonjameyer]

Summary

This PR adds a new Oracle APEX skill domain focused on APEX workspace administration, deployment, monitoring, and security workflows.

The APEX skill is structured around a token-optimized root apex/SKILL.md that routes to focused topic files on demand. It includes workspace lifecycle guidance, parsing schema guardrails, APEX user handling, deployment checks, patching workflows, monitoring patterns, MCP availability handling, and security review checklists.

Highlights

• Adds APEX workspace provisioning, listing, schema mapping, user creation, and removal guidance.
• Adds safety guardrails for destructive workspace cleanup, including exact English confirmation prompts.
• Adds recovery behavior for interrupted provisioning workflows, including artifact inventory and rollback confirmation.
• Adds parsing schema checks to avoid ORDS, APEX platform, admin, and service accounts.
• Adds existing-schema privilege validation, including conditional CREATE MLE and EXECUTE DYNAMIC MLE expectations for Oracle AI Database 26ai when MLE is needed.
• Adds APEX deployment topics for pre-checks, export/import review, post-deploy validation, and patching.
• Adds monitoring topics for activity logs, errors, background jobs, REST Data Sources, page performance, IR/IG tuning, AWR/wait correlation, and MCP availability.
• Adds security topics for guardrails, safety messages, audit columns, and security review.
• Adds apex/test-apex-skills.sh to validate APEX skill structure, routing, safety rules, DB-skill handoffs, and prompt examples.
• Updates the README to document the new APEX domain and its token-optimized design.
• uses DB skills instead of duplicating skills with a comment working now in db skills
• Clarified that directory naming and structure are aligned with related projects so they complement each other without conflicts.

[ORAsonjameyer]

superseeded by #52