feat(web): caption approval before FetLife email publish

[dhirmadi]

Description

Allow web UI users to review, edit, and confirm AI-generated captions before publishing to FetLife via email. Previously, clicking "Publish" re-ran AI caption generation from scratch, discarding the caption the user had reviewed after "Analyze & Caption". The FetLife email was sent with a caption the user never approved.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🔧 Configuration change
• 🎨 Code style update (formatting, renaming)
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• ✅ Test update
• 🔒 Security fix

Related Issue

Addresses user feedback: "cannot approve the caption needed to send emails to FetLife before publishing."

Changes Made

• workflow.py: Added caption_override parameter to WorkflowOrchestrator.execute(). When provided (and non-whitespace), skips AI caption generation and uses the override. Logs caption_override_used for audit trail.
• models.py: Added optional caption field to PublishRequest (backward-compatible, defaults to None).
• app.py: Route handler extracts and normalizes body.caption (whitespace-only → None), passes through to service.
• service.py: publish_image() accepts caption_override and forwards to orchestrator. Logs when override is received.
• index.html (CSS): Textarea styling, character counter, edited badge — all matching existing dark theme.
• index.html (HTML): Replaced read-only caption <div> with editable <textarea>, added N / 240 character counter and "(edited)" indicator.
• index.html (JS): Updated setCaption() for textarea, added updateCaptionMeta() with live counter, added XSS-safe inline confirmation modal (showPublishConfirm()), updated apiPublish() to send caption in POST body.
• test_workflow_feature_toggles.py: 5 new tests — override happy path, empty string fallthrough, whitespace-only fallthrough, sanitization by format_caption, and None preserving default behavior. Enhanced _StubPublisher to capture received captions.
• test_web_app_additional.py / test_web_service.py: Updated stubs to accept new caption_override parameter.

Testing

• All existing tests pass (448 passed, 0 failed)
• Added new tests for new functionality (5 tests)
• Tested manually with the following scenarios:
  • Publish with AI-generated caption (no edit) — caption sent as-is
  • Edit caption, confirm, publish — edited caption used, AI skipped
  • Cancel confirmation modal — publish aborted
  • Empty/whitespace caption falls through to AI generation
  • Character counter turns red above 240 chars
  • "(edited)" badge appears when caption is modified

Security Considerations

• No sensitive data exposed in code or logs (caption length logged, not content)
• Credentials properly handled (not hardcoded)
• Input validation added where necessary (whitespace normalization, server-side format_caption sanitization still enforced)
• No new security vulnerabilities introduced (confirmation modal uses textContent DOM API, not innerHTML — XSS-safe)

Checklist

• My code follows the project's code style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Additional Notes

• Backward-compatible: All existing callers (CLI, cron, orchestrator) that don't provide caption_override get the existing AI generation flow unchanged.
• Defense-in-depth: Caption normalization is guarded at three layers — frontend (isPlaceholder check), route handler (strip() or None), and workflow (caption_override.strip() check).
• Character counter is informational: The 240-char limit matches _MAX_LEN["email"] in captions.py. Server-side format_caption still enforces the hard trim — the counter provides user feedback, not the enforcement.
• Out of scope: Caption editing for non-email platforms, caption history/undo, hard client-side length block.