[trading-bot] Remove ollama refs from commented-out source

## Context
Stage 5 of ollama decommission. The `trading-bot` stack has been entirely
commented out since 2026-04-06 (deployments scaled to 0, infra disabled to
prevent re-creation on apply). The commented body still contained references
to `var.ollama_host`, `TRADING_OLLAMA_HOST`, and `TRADING_OLLAMA_MODEL`.
Removing them now so if/when the stack is ever re-enabled, those dead
references don't need remembering.

## This change
- Removes `variable "ollama_host"` from the commented-out block.
- Removes `TRADING_OLLAMA_HOST` and `TRADING_OLLAMA_MODEL` from the
  commented `common_env` locals.
- Verified the outer `/* ... */` comment block still wraps the entire stack
  (head: `/*`, tail: `*/`).
- No apply needed — stack is disabled.

## Test plan
### Automated
- None — file content is inside a block comment; Terraform parser ignores it.
- `terraform fmt` check: no effect (commented content).

### Manual Verification
- `head -1 stacks/trading-bot/main.tf` → `/*`
- `tail -1 stacks/trading-bot/main.tf` → `*/`

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

stacks/trading-bot/main.tf

@@ -10,7 +10,6 @@ variable "tls_secret_name" {
 variable "nfs_server" { type = string }
 variable "postgresql_host" { type = string }
 variable "redis_host" { type = string }
-variable "ollama_host" { type = string }
 locals {
   common_env = {
     TRADING_REDIS_URL                    = "redis://${var.redis_host}:6379/4"
@@ -18,8 +17,6 @@ locals {
     TRADING_ALPACA_BASE_URL              = "https://paper-api.alpaca.markets"
     TRADING_PAPER_TRADING                = "true"
     TRADING_REDDIT_USER_AGENT            = "trading-bot/0.1"
-    TRADING_OLLAMA_HOST                  = "http://${var.ollama_host}:11434"
-    TRADING_OLLAMA_MODEL                 = "gemma3"
     TRADING_WATCHLIST                    = "[\"AAPL\",\"TSLA\",\"NVDA\",\"MSFT\",\"GOOGL\"]"
     TRADING_BAR_TIMEFRAME                = "5Min"
     TRADING_POLL_INTERVAL_SECONDS        = "60"