fix(config_edit): stop write-back from adding CRs to multi-line attributes

[s31teg]

Problem

Every save through ConfigEditor::to_bytes() added one carriage return per line break inside attribute values, so multi-line attributes degraded a little more with each lox config edit.

Loxone writes CRLF line endings but keeps line breaks inside attribute values as they are: bare LF in note text (Text="…"), CRLF in AutoPilot rule JSON (APC="…"). The CRLF post-process replaced every \n in the output, including those inside attributes. On the next load xml-rs kept the \r and re-emitted it as 
, so:

• note *****\nOLD ON TRIGGERS became *****




\r\nOLD ON TRIGGERS after five lox config layout calls
• AutoPilot rule JSON accumulated \r characters the same way

Fix

• Convert LF → CRLF only outside start tags (to_crlf_outside_attrs), skipping comments, CDATA and processing instructions, mirroring normalize_loxone_xml.
• Restore 
 alongside 
 in normalize_start_tag, so attribute values round-trip exactly as read (bare LF stays LF, CRLF stays CRLF).

Testing

• New regression test test_crlf_file_keeps_lf_in_attr_values_across_saves: a Loxone-style file (BOM, CRLF, LF in note text, CRLF in AutoPilot JSON) is byte-identical after one and two saves. It fails on main and passes with this change.
• cargo fmt --check, cargo clippy -- -D warnings, cargo build --release and cargo test all pass.
• Checked on a real 2.4 MB project: a no-op save is byte-identical to the input, and lox config layout --only-new now changes only block coordinates (previously it also rewrote 59 notes and 2 AutoPilot rules).