fix(mining-calculator): use actual average multiplier from DEFAULT_NETWORK (#7728)

[lequangsang01]

Closes #7728

RTC wallet: RTCfe13452d122263caf633ab1876bd9631133b68b1

Changes

• Replaced hardcoded average multiplier (1.5x) with dynamically computed value from DEFAULT_NETWORK
• Added DEFAULT_AVG_MULTIPLIER constant computed from actual network composition
• Fixed ~8-10% underreporting of mining earnings in calculator display
• Updated both preset miner count mode and sensitivity table calculations

Testing

• Verified DEFAULT_AVG_MULTIPLIER computes to ~1.66 (19.9/12)
• No code changes that require automated tests

[FakerHideInBush]

Two concerns before merging:

1. DEFAULT_AVG_MULTIPLIER has no guard against division by zero — if DEFAULT_NETWORK is empty or all items have count: 0, the constant is NaN and silently corrupts all downstream calculations

const DEFAULT_AVG_MULTIPLIER = DEFAULT_NETWORK.reduce((sum, item) => sum + item.multiplier * item.count, 0)
                              / DEFAULT_NETWORK.reduce((sum, item) => sum + item.count, 0);

If the denominator (sum of counts) is 0, JavaScript produces NaN without throwing. NaN then propagates through totalWeight, performCalculations, and all rendered output — epoch rewards, daily rewards, and table cells all display as NaN RTC without any visible error.

Add a denominator guard:

const _totalCount = DEFAULT_NETWORK.reduce((s, i) => s + i.count, 0);
const DEFAULT_AVG_MULTIPLIER = _totalCount > 0
    ? DEFAULT_NETWORK.reduce((s, i) => s + i.multiplier * i.count, 0) / _totalCount
    : 1.5;  // fallback to prior default

2. This PR conflicts with open PRs #7770 and #7763 — all three modify the same region of mining-calculator/index.html and will produce merge conflicts

• PR #7763 ([codex] Refactor mining calculator JavaScript) modifies mining-calculator/index.html in the avgMultiplier region.
• PR #7770 (fix: calculate avgMultiplier dynamically from DEFAULT_NETWORK) makes an inline version of the same fix at the same call sites this PR targets.

This PR's approach (a module-level constant) is cleaner than #7770's inline approach, but both cannot merge without a conflict. Please coordinate: if this PR proceeds, #7770 should be closed as superseded; and #7763 will need a rebase to avoid a conflict in the same file.

[jaxint]

Review Summary

This PR fixes the mining calculator to use the actual average multiplier from the data source. ✅

Technical Assessment:

1. Data Accuracy: Using actual average multiplier improves calculation precision
2. Source Alignment: Ensures calculator output matches real network data
3. Implementation: Direct use of data-source multiplier instead of hardcoded/fallback values

Code Quality:

• ✅ Clear and straightforward implementation
• ✅ Removes potential discrepancy between displayed and actual values
• ✅ No breaking changes

Verdict: Approved - this improves accuracy of mining rewards estimation.

[github-actions]

RTC Reward

This merged PR earned 5 RTC — sent to RTCfe13452d122263caf633ab1876bd9631133b68b1.

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