Plan 02: Move Favicon Cooldown to Source Model

Objective

Move favicon cooldown clearing logic from SourceFaviconFetchesController into the Source model (C2), following the project convention that business logic lives in models.

Context

• app/controllers/source_monitor/source_favicon_fetches_controller.rb:33-36 has clear_favicon_cooldown that directly manipulates metadata hash and calls update_column
• app/models/source_monitor/source.rb already has attribute :metadata, default: -> { {} } (line 35)
• FaviconFetchJob also checks favicon_last_attempted_at in metadata -- having the clear method on the model centralizes this concern
• The controller bypasses model callbacks with update_column -- the model method should preserve this behavior (it's intentional for cooldown clearing)

Tasks

Task 1: Write Source#clear_favicon_cooldown! tests (TDD red)

Add tests to test/models/source_monitor/source_test.rb:

• Test clears favicon_last_attempted_at from metadata when key exists
• Test is a no-op when key is not present (no error)
• Test handles nil metadata gracefully
• Test preserves other metadata keys

Task 2: Add clear_favicon_cooldown! to Source model

Add to app/models/source_monitor/source.rb:

def clear_favicon_cooldown!
  metadata_without_cooldown = (metadata || {}).except("favicon_last_attempted_at")
  update_column(:metadata, metadata_without_cooldown)
end

Task 3: Update SourceFaviconFetchesController

In app/controllers/source_monitor/source_favicon_fetches_controller.rb:

• Replace clear_favicon_cooldown(@source) with @source.clear_favicon_cooldown!
• Remove the private clear_favicon_cooldown method

Task 4: Verify

• bin/rails test -- all pass
• bin/rubocop -- zero offenses