fix(analytics): convert decimal channel hashes to hex format in UI

[Jeymz]

Summary

fixes #190

The Hash column in Analytics → Channels showed decimal values (17, 129) instead of hexadecimal.

Root cause

channelRowHtml in public/analytics.js only formatted the hash as hex when c.hash was a JavaScript number. /api/analytics/channels sends it as a decimal string ("17"), so it took the fallback branch and was printed as-is. The Go tests assert this string format (channel_analytics_test.go), so the API is unchanged and the fix is in the frontend.

Changes

public/analytics.js

• Added channelHashNum(h), which turns a number or an all-digits string into a number and returns NaN for anything else.
• Added formatChannelHash(h), which renders 0xNN (uppercase, zero-padded to 2 digits) for numeric values. Non-numeric ids such as enc_A1B2 pass through esc(). They were previously printed unescaped.
• channelRowHtml uses formatChannelHash(c.hash) for the Hash cell.
• The hash case in sortChannels compares numerically when both hashes are numeric, so the order is 0x05 < 0x11 < 0x81. Previously decimal strings sorted as text. Non-numeric hashes keep the old string compare.
• The #/channels?ch=<hash> deep link still uses the decimal value, so existing bookmarks keep working.

tests/unit/test-frontend-helpers.js

• "17", "129" and "5" render as 0x11, 0x81 and 0x05. Decimal is not displayed, and the deep link keeps ?ch=17.
• enc_A1B2 is unchanged and <b> is HTML-escaped.
• The hash sort is numeric for decimal-string hashes.

Testing

• node tests/unit/test-frontend-helpers.js: 729 passed, 0 failed.
• No Go files changed.
• Not yet done: browser validation of Analytics → Channels

Performance

No hot-path impact. This is one regex and one toString(16) per rendered row, and the sort comparator does a cheap parse per comparison.

Follow-ups (not in this PR)

• Send the hash as a typed integer, or add a hashHex field, so clients stop converting a string themselves. This is a good moment to move the channels analytics response to a named struct, in line with the map[string]interface{} rule in AGENTS.md.
• Check whether public/channels.js shows the same decimal value anywhere.

[ITblacksheep]

Can you go ahead and open an enhancement to fix this on the backend also?

[Jeymz]

Can you go ahead and open an enhancement to fix this on the backend also?

Follow-up items documented in #193

[diffwireauto]

Human approval received from Strycher in session 64287058 ("Merge #192."). Re-validated against the remote immediately prior: state=OPEN, mergeable=MERGEABLE, mergeStateStatus=CLEAN, reviewDecision=APPROVED (ITblacksheep), head 7440c6b39465a803cd6d1baf79a5248c1cb426ac, base 448745c9 (current master, 0 commits behind).

Rebased earlier tonight onto the #194 staging fix. The rebase preserved content exactly — diff hash fbbbc2539e66dd6dd211a607176e3774ae439828 before and after — and kept Jeymz Simmons as commit author.