Modularize Go files, extract JS to static, implement competitor pricelists

Go refactoring:
- Split handlers/pricing.go (2446→291 lines) into 5 focused files
- Split services/stock_import.go (1334→~400 lines) into stock_mappings.go + stock_parse.go
- Split services/sync/service.go (1290→~250 lines) into 3 files

JS extraction:
- Move all inline <script> blocks to web/static/js/ (6 files)
- Templates reduced: admin_pricing 2873→521, lot 1531→304, vendor_mappings 1063→169, etc.

Competitor pricelists (migrations 033-039):
- qt_competitors + partnumber_log_competitors tables
- Excel import with column mapping, dedup, bulk insert
- p/n→lot resolution via weighted_median, discount applied
- Unmapped p/ns written to qt_vendor_partnumber_seen
- Quote counts (unique/total) shown on /admin/competitors
- price_method="weighted_median", price_period_days=0 stored explicitly

Fix price_method/price_period_days for warehouse items:
- warehouse: weighted_avg, period=0
- competitor: weighted_median, period=0
- Removes misleading DB defaults (was: median/90)

Update bible: architecture.md, pricelist.md, history.md

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

migrations/033_add_competitors.sql

@@ -0,0 +1,27 @@
+CREATE TABLE IF NOT EXISTS qt_competitors (
+    id                    BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    name                  VARCHAR(255) NOT NULL,
+    code                  VARCHAR(100) NOT NULL UNIQUE,
+    delivery_basis        VARCHAR(50)  NOT NULL DEFAULT 'DDP',
+    expected_discount_pct DECIMAL(5,2) NOT NULL DEFAULT 0.00,
+    column_mapping        JSON         NULL,
+    is_active             BOOLEAN      NOT NULL DEFAULT TRUE,
+    created_at            TIMESTAMP    NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at            TIMESTAMP    NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+);
+
+CREATE TABLE IF NOT EXISTS partnumber_log_competitors (
+    id              BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    competitor_id   BIGINT UNSIGNED NOT NULL,
+    lot_name        VARCHAR(255)    NOT NULL,
+    raw_partnumber  VARCHAR(255)    NULL,
+    price           DECIMAL(12,2)   NOT NULL,
+    quote_date      DATE            NOT NULL,
+    created_at      TIMESTAMP       NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    INDEX idx_plc_competitor_id (competitor_id),
+    INDEX idx_plc_lot_name (lot_name),
+    INDEX idx_plc_competitor_lot_date (competitor_id, lot_name, quote_date),
+    CONSTRAINT fk_plc_competitor
+        FOREIGN KEY (competitor_id) REFERENCES qt_competitors(id)
+        ON DELETE RESTRICT ON UPDATE CASCADE
+);