fix: address potential panics in Result-returning functions (#432)

[chairulakmal]

Summary

Addresses issue #432 (Case 1): reviews unwrap/expect calls in functions that return a Result.

Converted to error propagation:

• lists.rs — into_content_blocking() now uses try_for_each + ok_or instead of expect, so a missing raw_line returns Err rather than panicking.
• resources/resource_storage.rs — get_scriptlet_resource() now returns a new InvalidScriptletArgs error instead of unwrapping parse_scriptlet_args(). Malformed scriptlet args (e.g. an unclosed quote) no longer panic. Added a regression test.

Documented remaining safe panics with explanatory comments (abstract_network.rs, url_parser/parser.rs, regex_manager.rs, blocker.rs, cosmetic_filter_cache_builder.rs).

Does not overlap with #662, which covers content_blocking.rs.

Tests

cargo test --lib and cargo test --lib --features content-blocking pass; cargo clippy --features content-blocking -- -D warnings is clean.