[Describe the pull request here...]

no don't make me use wordpress for seo no please no please don't make me do it

Changes:

1. Subdirectory Support

• Added subdirectory config option in config.ini, allowing WriteFreely to be hosted at a path prefix (e.g. example.com/blog/).
• New AppCfg methods on the config struct:
  • SubdirectoryPath() — normalizes the configured subdir path
  • PrefixPath(path) — prepends the subdir prefix to any local path
  • AbsoluteURL(path) — builds a full absolute URL
  • AbsoluteHost() — returns the canonical host (with subdir stripped)
• All routes, templates, and rendering logic updated to use these helpers so links and asset URLs are correct under a subdir deployment.
• All templates updated to use a {{subdir}} template variable for asset and navigation paths.
• Font and icon CSS paths corrected for subdir hosting (less/fonts.less, less/icons.less).
• Tests added in collections_subdir_test.go to validate path generation.

2. ActivityPub / Federation Improvements

• Introduced ExtendedPerson struct wrapping the upstream activitystreams.Person to add the image (banner/header) field, which is part of the AP spec and supported by Mastodon but absent from the upstream library.
• PersonObject() now populates the following fields from collection settings:
  • icon — avatar/profile picture
  • image — header/banner image
  • name — display name
  • summary — bio/description
• New federateActor() function sends an Update{Person} activity to all followers whenever a collection's profile is updated, so changes to bio, display name, avatar, and header propagate to Mastodon and other ActivityPub servers in real time.
• collections.go now calls federateActor after saving collection metadata.
• All ActivityPub activity posts use AbsoluteHost() to ensure correct absolute URLs.

3. Mermaid Diagram Rendering

• Added static/js/mermaid.min.js — bundled locally, no CDN dependency.
• templates/include/post-render.tmpl gains a {{define "mermaid"}} block that:
  • Detects <code class="language-mermaid"> blocks in rendered posts
  • Replaces them with <div class="mermaid"> elements
  • Lazy-loads the Mermaid library from {{subdir}}/js/mermaid.min.js
  • Calls mermaid.initialize() and mermaid.run()
  • Post-processes SVG text colors for theme consistency
• Works correctly under subdirectory deployments via the {{subdir}} prefix.

4. Additional Fixes

• Mailer: SSL/TLS support added (mailer/mailer.go, email.go).
• Markdown rendering: Removed dead alterShortCodeEmailSubForm helper and spam honeypot injection from the live preview render endpoint.
• Base URLs: Fixed relative vs. absolute base URL construction in postrender.go — removed leading / that caused double-slashes with the subdir prefix.
• Chorus mode: Hashtag prefix now uses cfg.App.PrefixPath("/read/t/") and mention prefix uses cfg.App.AbsoluteURL("/@/") for correct subdir-aware URLs.

5. Test Coverage

Significant new tests added across:

Photo Examples:

Mermaid Rendering in blog post

Branding Settings

Mermaid Setting

• I have signed the CLA