fix: address critical correctness, reliability, and design issues in pipeline

CORRECTNESS FIXES:
- json_loader: Add RollbackTransaction() and call it on exception instead of
  CommitTransaction(). Prevents partial data corruption on parse/disk errors.
- wikipedia_service: Fix invalid MediaWiki API parameter explaintext=true ->
  explaintext=1. Now returns plain text instead of HTML markup in contexts.
- helpers: Fix ParseTwoLineResponse filter to only remove known thinking tags
  (<think>, <reasoning>, <reflect>) instead of any <...> pattern. Prevents
  silently removing legitimate output like <username>content</username>.

RELIABILITY & DESIGN IMPROVEMENTS:
- load/main: Make n_ctx (context window size) configurable via --n-ctx flag
  (default 2048, range 1-32768) to support larger models like Qwen3-14B.
- generate_brewery: Prevent retry prompt growth by extracting location context
  into constant and using compact retry format (error + schema + location only).
  Avoids token truncation on final retry attempts.
- database: Fix data representativeness by changing QueryCities from
  ORDER BY name (alphabetic bias) to ORDER BY RANDOM() for unbiased sampling.
  Convert all SQLITE_STATIC to SQLITE_TRANSIENT to prevent use-after-free risks.

POLISH:
- infer: Advance sampling seed between generation calls to improve diversity
  across brewery and user generation.
- data_downloader: Remove unnecessary commit hash truncation; use full hash.
- json_loader: Fix misleading log message from "RapidJSON" to "Boost.JSON".

pipeline/src/data_generation/llama/generate_brewery.cpp

@@ -50,6 +50,14 @@ BreweryResult LlamaGenerator::GenerateBrewery(
             ? std::string(".")
             : std::string(". Regional context: ") + safe_region_context);
 
+   /**
+    * Store location context for retry prompts (without repeating full context)
+    */
+   const std::string retry_location =
+       "Location: " + city_name +
+       (country_name.empty() ? std::string("")
+                             : std::string(", ") + country_name);
+
    /**
     * RETRY LOOP with validation and error correction
     * Attempts to generate valid brewery data up to 3 times, with feedback-based
@@ -84,19 +92,16 @@ BreweryResult LlamaGenerator::GenerateBrewery(
       spdlog::warn("LlamaGenerator: malformed brewery JSON (attempt {}): {}",
                    attempt + 1, validation_error);
 
-      // Update prompt with error details to guide LLM toward correct output
+      // Update prompt with error details to guide LLM toward correct output.
+      // For retries, use a compact prompt format to avoid exceeding token
+      // limits.
       prompt =
           "Your previous response was invalid. Error: " + validation_error +
           "\nReturn ONLY valid JSON with this exact schema: "
           "{\"name\": \"string\", \"description\": \"string\"}."
           "\nDo not include markdown, comments, or extra keys."
-          "\n\nLocation: " +
-          city_name +
-          (country_name.empty() ? std::string("")
-                                : std::string(", ") + country_name) +
-          (safe_region_context.empty()
-               ? std::string("")
-               : std::string("\nRegional context: ") + safe_region_context);
+          "\n\n" +
+          retry_location;
    }
 
    // All retry attempts exhausted: log failure and throw exception