fix(alerter): escape all dynamic numeric fields in Telegram MarkdownV2

Telegram's MarkdownV2 parser treats `.` as a special character and rejects
the message with `Bad Request: can't parse entities` if any unescaped `.`
appears outside a code or pre block. The current formatter only escapes
the static `Market:` title and the `$` in the USDC amount, while leaving
three numeric runs unescaped:

  *Risk Score:* 0.82 (HIGH)            ← `.` in the score literal
  *Trade:* BUY Yes @ $0.075 | $15,000.00
                       ↑                  ↑
                       price              USDC amount

In production this means well-formed alerts silently fail to reach
Telegram users — the dispatcher reports a 400 from the Bot API and the
event is dropped.

This change routes every dynamic value through `_escape_telegram_markdown`
before interpolation:

  - `assessment.weighted_score` (risk score)
  - `trade.price` (price string)
  - `format_usdc(trade.notional_value)` (USDC amount, including its `.`)
  - `trade.side` and `trade.outcome` (defensive — upstream values may
    contain `-` or `.` in future schema changes)

The test that previously asserted `"0.82" in result.telegram_markdown` is
updated to require the escaped form `"0\.82"`, and a new test pins down
that none of `0.82` / `0.075` / `15,000.00` appear in unescaped form.

src/polymarket_insider_tracker/alerter/formatter.py

@@ -290,12 +290,14 @@ class AlertFormatter:
                     wallet_line += f" \\(Age: {age_hours:.0f}h\\)"
         lines.append(wallet_line)
 
-        # Risk score
-        lines.append(f"*Risk Score:* {assessment.weighted_score:.2f} \\({risk_level}\\)")
+        # Risk score — every numeric literal here must be escaped because
+        # MarkdownV2 treats `.` as a special character and rejects unescaped
+        # ones with `Bad Request: can't parse entities`.
+        score_str = self._escape_telegram_markdown(f"{assessment.weighted_score:.2f}")
+        lines.append(f"*Risk Score:* {score_str} \\({risk_level}\\)")
 
         # Market
         market_title = trade.event_title or trade.market_slug or "Unknown Market"
-        # Escape special Telegram markdown characters
         market_title_escaped = self._escape_telegram_markdown(market_title)
         if "market" in links:
             lines.append(f"*Market:* [{market_title_escaped}]({links['market']})")
@@ -303,14 +305,16 @@ class AlertFormatter:
             lines.append(f"*Market:* {market_title_escaped}")
 
         # Trade details
-        usdc_value = format_usdc(trade.notional_value).replace("$", "\\$")
-        lines.append(
-            f"*Trade:* {trade.side} {trade.outcome} @ \\${trade.price:.3f} \\| {usdc_value}"
-        )
+        usdc_value = self._escape_telegram_markdown(format_usdc(trade.notional_value))
+        price_str = self._escape_telegram_markdown(f"{trade.price:.3f}")
+        side_escaped = self._escape_telegram_markdown(trade.side)
+        outcome_escaped = self._escape_telegram_markdown(trade.outcome)
+        lines.append(f"*Trade:* {side_escaped} {outcome_escaped} @ \\${price_str} \\| {usdc_value}")
 
         # Signals
         if signals:
-            lines.append(f"*Signals:* {', '.join(signals)}")
+            signals_escaped = [self._escape_telegram_markdown(s) for s in signals]
+            lines.append(f"*Signals:* {', '.join(signals_escaped)}")
 
         # Links
         lines.append("")