Require explicit FreshRSS host and credentials; remove localhost fallback

[Skulldorom]

Motivation

• Prevent containers from entering a restart loop when FreshRSS connection info is missing by failing early with a clear error.
• Remove the unsafe http://localhost:8020 fallback which is not reachable from inside the container in most deployments.
• Provide documentation and examples for common deployment networking patterns so users can choose the correct host value.

Description

• Updated docker-compose.yml to require FRESHRSS_HOST, FRESHRSS_USER, and FRESHRSS_PASS using Compose interpolation (${FRESHRSS_HOST:?...}) so missing or empty values produce a clear error before container creation.
• Replaced the http://localhost:8020 default with explicit guidance and examples in .env.example, adding options for a same-project Compose service, Docker Desktop (host.docker.internal), and Linux host addresses (or host-gateway mapping).
• Expanded README.md with instructions explaining that FRESHRSS_HOST must be reachable from the API container and added illustrative Compose and .env snippets for the three deployment cases.
• Clarified docker compose usage in the README and replaced ambiguous examples that encouraged using localhost from inside containers.

Testing

• Ran git diff --check with no issues reported.
• Ran the test suite with uv run pytest and all tests passed (9 passed).
• Attempted to validate Docker Compose behavior (docker compose config) but Compose/Docker was not available in the execution environment so validation could not be executed here.

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add FreshRSS before using its service hostname

This “equivalent” setup fails when a user keeps the provided Compose file: docker-compose.yml defines only custom-api and joins no external network, so Docker DNS cannot resolve the freshrss hostname. This option must also instruct the user to add the FreshRSS service to that Compose project or attach both containers to a shared network; changing only .env causes every FreshRSS request to fail.

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