docs: sweep example LAN IPs to RFC-5737 documentation range

Phase 4 of the docs portion of the rfc-5737-cleanup. Replaces all
192.168.1.x example IPs in tracked .md / .txt files with the
equivalent last-octet under 192.0.2.x.

192.168.1.x is RFC-1918 private space and routes on real networks,
which leaves readers guessing whether a documented IP is a placeholder
or a documented LAN. 192.0.2.0/24 is reserved by RFC 5737 exclusively
for documentation — readers know on sight that they're examples.

58 files touched, 551 line pairs. Includes .github issue/PR templates,
all docs/ references, example READMEs, and one script doc. No code
changes, no test changes; test files still carry the 192.168.1.x
placeholder pending Phase 2 in _/RFC-5737-cleanup/assessment.md.

Also fixed a small fallout in docs/analysis/ANONYMIZATION-SUMMARY.md
where the explanatory sentence "a reader can't tell whether
192.168.1.10 is a placeholder or a documented LAN address" had
itself been swept by the regex (inverting the point); restored the
literal example and noted the sweep progress inline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/pull_request_template.md

@@ -50,7 +50,7 @@ Please check the type of change your PR introduces:
 
 **Device(s) tested with:**
 - Device model: [e.g. SoundTouch 10]
-- Device IP: [e.g. 192.168.1.100]
+- Device IP: [e.g. 192.0.2.100]
 - Test results: [brief description]
 
 ### Test Commands
@@ -58,7 +58,7 @@ Please check the type of change your PR introduces:
 # Commands used to test this change
 make test
 go test ./pkg/client -v -run TestNewFeature
-soundtouch-cli --host 192.168.1.100 new-command
+soundtouch-cli --host 192.0.2.100 new-command
 ```
 
 ## Documentation