fix(macro): replace hardcoded BTC mining thresholds with Mayer Multiple (#750)

* fix(macro): replace hardcoded BTC mining thresholds with Mayer Multiple

The $60k/$40k thresholds were calibrated for 2023 BTC prices and
always return 'PROFITABLE' at current price levels. Use the Mayer
Multiple (price/SMA200) instead — this adapts to any price regime.

Falls back to dollar thresholds only when SMA200 is unavailable.

Addresses #197 (L-11).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor(macro): rename Mining Cost → Price Momentum, use Mayer Multiple

- Replace hardcoded $60k/$40k thresholds with Mayer Multiple (price/SMA200)
- Reuse existing `mayerMultiple` variable instead of recomputing
- Remove stale hashChange guard — momentum doesn't depend on hashrate
- Drop dollar fallback; return UNKNOWN when SMA200 unavailable
- Rename signal: MiningCost → PriceMomentum, statuses: STRONG/MODERATE/WEAK
- Update proto, OpenAPI specs, generated types, frontend panel, all locales

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Elie Habib <elie.habib@gmail.com>

docs/api/EconomicService.openapi.yaml

@@ -528,8 +528,8 @@ components:
                     $ref: '#/components/schemas/TechnicalTrendSignal'
                 hashRate:
                     $ref: '#/components/schemas/HashRateSignal'
-                miningCost:
-                    $ref: '#/components/schemas/MiningCostSignal'
+                priceMomentum:
+                    $ref: '#/components/schemas/PriceMomentumSignal'
                 fearGreed:
                     $ref: '#/components/schemas/FearGreedSignal'
             description: MacroSignals contains all 7 individual signal computations.
@@ -624,13 +624,13 @@ components:
                     format: double
                     description: Hash rate change over 30 days as percentage.
             description: HashRateSignal tracks Bitcoin hash rate momentum.
-        MiningCostSignal:
+        PriceMomentumSignal:
             type: object
             properties:
                 status:
                     type: string
-                    description: '"PROFITABLE", "TIGHT", "SQUEEZE", or "UNKNOWN".'
-            description: MiningCostSignal estimates mining profitability from BTC price thresholds.
+                    description: '"STRONG", "MODERATE", "WEAK", or "UNKNOWN".'
+            description: PriceMomentumSignal uses the Mayer Multiple (price/SMA200) as a market-adaptive signal.
         FearGreedSignal:
             type: object
             properties: