🎨 Polish login password visibility toggle

[ebigunso]

Summary

• replace the login password Show/Hide text button with prepared eye icons
• make the toggle styling cleaner and theme-aware, including consistent hover behavior
• record the execution notes and approval-gate lesson for this change

Validation

• cd sleep-ui && npm run check
• cd sleep-ui && npm run test:unit
• reviewer evidence captured for login toggle light/dark states under .playwright-cli/

[Copilot]

Pull request overview

Updates the login password visibility toggle in sleep-ui from a text-based control to an icon-based control, with theme-aware styling, and records the associated execution/lesson documentation.

Changes:

• Add eye / eye-slashed SVG assets and render them via CSS masking for the login password toggle.
• Update login page markup and shared CSS to support the new icon toggle styling and spacing.
• Add a completed execution plan and a workflow/approval-gate lesson entry documenting the process.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
sleep-ui/static/icons/eye.svg	Adds the “eye” icon asset used for the visibility toggle.
sleep-ui/static/icons/eye-slashed.svg	Adds the “eye slashed” icon asset used for the visibility toggle.
sleep-ui/src/routes/login/+page.svelte	Replaces Show/Hide text with an icon span and updates input padding class.
sleep-ui/src/app.css	Introduces icon-mask styling and updated button sizing/hover/focus behavior.
docs/coding-agent/plans/completed/login-password-visibility-icons-plan.md	Records the implementation plan, validations, and reviewer evidence.
docs/coding-agent/lessons.md	Adds a lesson about not inferring approval from requirement clarifications.

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