Render Liquid fields by default

[caitmich]

Problem

Liquid template tags in field values (e.g. `{{ project.name }}` in a Title or Description field) were not evaluated automatically. Each view that wanted rendered output had to opt in explicitly — calling a helper, passing assigns, or wiring up a filter. This led to inconsistent behaviour: the same field could appear raw in one place and rendered in another, and new views silently showed unrendered templates.

Solution

Render-by-default: `fields` and `title` on models always return Liquid-evaluated values in request contexts. `raw_fields` is the explicit escape hatch, used only when editing, diffing, or writing to the database.

Three moving parts:

1. LiquidRenderContext (app/lib/liquid_render_context.rb, new)

• Thread-local context holder with `set`, `clear`, `current`, and `render`.
• Controllers store a lazy proc before the action runs; `render` resolves it on first use — after all `before_action`s have run and instance variables are set (so that liquid_resource_assigns has been set).
• Errors from Liquid evaluation fall back to the raw value rather than raising.

2. `HasFields#dradis_has_fields_for`

• raw_fields contains the existing parser logic, unchanged.
• fields renders via LiquidRenderContext.render when a context is present and memoizes the result on the instance.
• A reentrancy guard (@_rendering_fields) prevents infinite loops when a field value references the same record's fields via a drop (e.g. {{ issue.fields['Impact'] }} inside another field).
• set_field and delete_field write through raw_fields so rendered output is never saved back to the database.
• title inherits rendering automatically since it delegates to fields.fetch('Title', ...).

3. LiquidEnabledResource + ProjectScoped

• with_liquid_render_context lives in LiquidEnabledResource, which is now included by ProjectScoped. All project-scoped controllers get Liquid rendering automatically. Non-project controllers that need it (e.g. MarkupController) include LiquidEnabledResource directly.

DiffedContent is updated to use raw_fields so sync and diff operations always work on raw Liquid templates.

Testing Steps

• Field containing `{{ project.name }}`: renders correctly in index tables, show headings, breadcrumbs, and page `<title>`
• Field containing cross-field references (e.g. `{{ issue.fields['Impact'] }}`): reentrancy guard prevents infinite loops, raw value returned as fallback
• Edit form shows the raw Liquid template (form binds to `:text`, not `fields`)
• Background and API contexts never set a `LiquidRenderContext`, so `fields` returns raw values — no behaviour change for jobs or API consumers

Check List

• Added a CHANGELOG entry
• Commit message has a detailed description of what changed and why.