fix: idle WebSocket connections are dropped after 30 seconds

[oleksandr-nc]

While investigating #114 I found that idle WebSocket connections through HaRP are closed after exactly 30 seconds: the config defines no timeout tunnel, so after the 101 upgrade HAProxy falls back to timeout client for the tunnel, and any ExApp WebSocket that does not ping more often than that gets cut (termination flags cD-- in the access log).

This adds timeout tunnel, configurable through a new HP_TIMEOUT_TUNNEL variable that defaults to the value of HP_TIMEOUT_SERVER (1800s), so raising the server timeout keeps tunnels covered too. Setting it to 0 means unlimited: HAProxy has no infinite value for this timeout (a literal timeout tunnel 0 silently falls back to the client timeout again, verified live), so start.sh maps 0 to HAProxy's 24d maximum. Also adds timeout client-fin 30s so half-closed tunnels are reaped quickly instead of lingering for the whole tunnel timeout.

Tested live against a probe ExApp connected through a real FRP tunnel: on the current release an idle WebSocket dies at 30.0s; with this change it survives 120s of idle with the default, an explicit HP_TIMEOUT_TUNNEL=15s cuts it at 15s, and 0 keeps it alive. SSE streams (idle, headers-only, with pings), slow responses and the 30s request-phase client timeout all behave exactly as before.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 550476c4-309a-48f4-8050-ef6fec73a44e

📥 Commits

Reviewing files that changed from the base of the PR and between 0326225 and 8a42b37.

📒 Files selected for processing (2)

• README.md
• start.sh

📝 Walkthrough

Walkthrough

Added HP_TIMEOUT_TUNNEL initialization, zero-value normalization, and export in start.sh. Configured HAProxy tunnel idle and client-fin timeouts. Updated timeout documentation for client inactivity, streaming responses, and upgraded connections.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: preventing idle WebSocket connections from being dropped after 30 seconds.
Description check	✅ Passed	The description clearly explains the timeout issue, configuration changes, default behavior, and testing results.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 2

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: f4d7d8f9-cdbd-4ac6-8325-3a716ba5e646

📥 Commits

Reviewing files that changed from the base of the PR and between ac0f3f4 and 0326225.

📒 Files selected for processing (3)

• README.md
• haproxy.cfg.template
• start.sh