Allow on-the-fly updates to adaptors, schemas, and icons

[taylordowns2000]

Description

Enables on-the-fly updates to the adaptor registry, credential schemas, and adaptor icons without requiring an application restart. Superusers can trigger refreshes from a new Settings > Maintenance admin page, and a configurable Oban cron job (ADAPTOR_REFRESH_INTERVAL_HOURS) keeps them in sync automatically across clustered nodes.

Closes #3114
Closes #2209
Closes #325 (wow what a golden oldie!)
Closes #1996

Changes

• New modules: AdaptorIcons, CredentialSchemas, and AdaptorRefreshWorker — extract runtime refresh logic out of mix tasks into callable modules
• AdaptorRegistry — refactored GenServer state from a bare list to a map (%{adaptors, cache_path, local_mode}); added refresh/1, refresh_sync/1, and PubSub-based cross-node sync via adaptor:refresh topic
• MaintenanceLive — new LiveView under Settings with action buttons for each refresh operation, gated to superusers
• Mix tasks (install_adaptor_icons, install_schemas) — slimmed down to thin wrappers around the new modules
• Oban cron — AdaptorRefreshWorker runs on a configurable interval; skips in local adaptors mode; broadcasts to peer nodes on success
• Minor .env.example typo fixes

Validation steps

1. Clear you adaptor registry and credential schemas
2. Log in as a superuser
3. Note that you can't find adaptors
4. Note that you can't find credential schemas
5. Go to the admin dashbaord
6. Go to "Maintenance"
7. Click the buttons and check that the things come back!

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• I have performed an AI review of my code (we recommend using /review
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[codecov]

Codecov Report

❌ Patch coverage is 81.18280% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.34%. Comparing base (e7c8d51) to head (ec919db).

Files with missing lines	Patch %	Lines
lib/lightning_web/live/maintenance_live/index.ex	57.50%	17 Missing ⚠️
lib/lightning/adaptor_registry.ex	71.42%	8 Missing ⚠️
lib/lightning/adaptor_refresh_worker.ex	83.33%	4 Missing ⚠️
lib/lightning/config/bootstrap.ex	57.14%	3 Missing ⚠️
lib/lightning/application.ex	80.00%	1 Missing ⚠️
lib/lightning/credential_schemas.ex	97.43%	1 Missing ⚠️
lib/mix/tasks/install_adaptor_icons.ex	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4473      +/-   ##
==========================================
- Coverage   89.47%   89.34%   -0.13%     
==========================================
  Files         425      429       +4     
  Lines       20212    20326     +114     
==========================================
+ Hits        18085    18161      +76     
- Misses       2127     2165      +38     

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