refactor: modular architecture v3.0 + SEC filing viewer fix + README

Architecture (3,909-line monolith → 28 focused modules, all < 300 lines):
- config/: constants.py (company lists, row maps, Damodaran baselines), theme.py (CSS/HTML)
- utils/: prefs, formatting, ticker, dcf, charts, ui_helpers
- data/: sec_parser, sec_fetcher, sec_downloader, financials, fundamentals,
         valuation, ratios, scores, scores_ai, market
- ai/: gemini_core, gemini_sec, gemini_insights
- views/: sidebar, tab1_quant, tab1_ai, tab1_filings, tab2_dcf,
          tab3_comps, tab4_news, tab5_markets, tab6_crypto, tab7_technical
- app.py: thin orchestrator (~118 lines)
- Strict unidirectional dependency graph (no circular imports)
- All @st.cache_data TTLs and st.session_state keys preserved identically

SEC filing viewer fix:
- Rebuilt EDGAR fetch chain: company_tickers.json → CIK → submissions API
  → filings.recent.primaryDocument[] (replaces deprecated directory.item)
- Filing type selectbox (10-K, 10-Q, 8-K, 20-F, 6-K) connected to backend
- Native HTML rendered via streamlit.components.v1.html() with CSS reset
- Errors surfaced explicitly with st.error()
- DART direct links restored for Korean-listed companies

.gitignore: data/ → data/*.json + data/*.html (preserve Python modules)
README: full rewrite for master's portfolio — 7-tab layout, architecture
diagram, modular structure tree, technical challenges, design rationale

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

utils/ticker.py

@@ -0,0 +1,37 @@
+"""
+Ticker formatting and market inference utilities.
+"""
+from config.constants import MARKET_OPTIONS
+
+
+def get_global_ticker(ticker: str, market: str) -> str:
+    """Format ticker for Yahoo Finance by market. US: as-is. South Korea: .KS or .KQ. Japan: .T. UK: .L. If ticker already has suffix, return as-is."""
+    if not (ticker or "").strip():
+        return (ticker or "").strip()
+    t = (ticker or "").strip()
+    if t.upper().endswith((".KS", ".KQ", ".T", ".L")):
+        return t
+    m = (market or "").strip()
+    if "US" in m or not m:
+        return t
+    if "Korea" in m or "KOSPI" in m or "KOSDAQ" in m:
+        return t + ".KS"
+    if "Japan" in m or "Nikkei" in m:
+        return t + ".T"
+    if "UK" in m or "LSE" in m:
+        return t + ".L"
+    return t
+
+
+def infer_market_from_ticker(ticker: str) -> str:
+    """Infer market label from ticker suffix (for Deep-Dive routing when no Market selector)."""
+    if not (ticker or "").strip():
+        return MARKET_OPTIONS[0]
+    t = (ticker or "").strip().upper()
+    if t.endswith(".KS") or t.endswith(".KQ"):
+        return "South Korea (KOSPI/KOSDAQ)"
+    if t.endswith(".T"):
+        return "Japan (Nikkei)"
+    if t.endswith(".L"):
+        return "UK (LSE)"
+    return "US (S&P/Dow/Nasdaq)"