feat: Rich text editor integration for Global Variables & Shortcodes plugins

[cp-bwg]

Summary

Adds rich text editor integration (Quill + TinyMCE) for the Global Variables plugin (PR #743) and a new Shortcodes plugin. This implements Part 2 (Rich Text Inline Tokens) from #719, which was explicitly planned as a follow-up in the original PR.

What This Enables

Global Variables — Editor Integration

• Quill: Custom VariableBlot renders {variable_key} tokens as styled blue chips in the editor
• TinyMCE: tinymce.PluginManager.add() registers a "Var" toolbar button with chip rendering
• Searchable picker dropdown fetches variables from /api/global-variables
• Token↔chip roundtrip: chips in editor → {key} in database → chips on reload
• Existing {key} text auto-converted to chips on content load

Shortcodes Plugin (New)

• [[shortcode_name param="value"]] syntax with registered handler functions
• Handler registry with built-in handlers: current_date, phone_link, cta_button, plan_count, provider_rating
• Server-side resolution via content:read hook (priority 60, runs after variables at 50)
• Full CRUD admin page with handler status badges and live preview
• Quill integration: purple ShortcodeBlot chips + "SC" toolbar button
• TinyMCE integration: PluginManager-based button with chip rendering

Shared Editor Utilities

• quill-shared.ts — Quill constructor Proxy (injects custom formats), searchable picker dropdown, enhancer polling framework
• tinymce-shared.ts — PluginManager approach (the official TinyMCE plugin API), picker dropdown, chip CSS injection into editor iframe
• admin-template.ts — Shared HTML wrapper with Tailwind + HTMX + CSRF auto-injection

Enhanced Admin Pages

• Both plugins have full CRUD admin pages (add, inline edit, delete, toggle active/inactive)
• "Rich Text Editor Integration" settings card with toggle + editor auto-detection
• Warning when no editor plugin is active

Related Issues

• Closes Feature: Dynamic content variables / inline tokens in rich text #719 (Part 2: Rich Text Inline Tokens)
• Extends PR feat: add dynamic content variables / inline tokens #743 (Part 1 + 3: Global Variables backend)

Technical Notes

• Editor scripts are self-contained HTML (styles + scripts) injectable via afterAuth middleware
• Quill: uses Proxy to patch constructor for custom format whitelisting
• TinyMCE: uses PluginManager.add() (official API) + server-side HTML replacement to inject button names into toolbar/plugins arrays
• Both editors support token↔chip serialization (editor DOM → DB tokens → editor DOM)
• Content resolution: variables (priority 50) → shortcodes (priority 60)
• Opt-out: ?resolve_variables=false, ?resolve_shortcodes=false