feat: Apply Odoo 16 coding guidelines across skill documentation

[piruin]

Summary

Apply the official Odoo 16 coding guidelines throughout the Odoo 16 skill pack while preserving version-specific runtime behavior and established addon conventions.

Changes

• Added coding conventions to the relevant Odoo 16 reference guides.
• Expanded module structure and filename guidance for models, controllers, wizards, security, reports, data files, and static assets.
• Consolidated JavaScript and CSS/SCSS conventions under the development guide's Static Assets Layout section.
• Clarified transaction, cursor, commit, rollback, savepoint, and retry guidance.
• Updated action, report, controller, manifest, ORM, security, translation, performance, and XML examples.
• Added the official Odoo 16 coding-guidelines source to SKILL.md.
• Removed an obsolete Odoo 16 review-plan document.

Validation (Local)

• JSON manifest validation: passed
• GitHub workflow YAML validation: passed
• npm test: passed using an LF-preserving, CI-equivalent checkout
• Skillspector static scan: passed
• git diff --check: passed

Source

• https://github.com/odoo/documentation/blob/16.0/content/contributing/development/coding_guidelines.rst

[piruin]

CI investigation:

• Only skill-security-scan failed. Validate, changelog-guard, and GitGuardian passed.
• The workflow installs the latest Skillspector from GitHub, currently skillspector 2.5.1.
• The repository's .skillspector-baseline.yaml uses baseline format version 1, but this Skillspector release requires version 2. The scan exits with:

  unsupported baseline version 1; expected 2

• The later skillspector.sarif upload error is secondary: the scan exited before generating the SARIF file.

This appears to be CI dependency/baseline drift rather than a failure caused by the Odoo 16 documentation changes in this PR. The shared CI fix is either to regenerate and review the baseline in version 2 format or pin Skillspector to a compatible revision.