feat: Replace cookiecutter with built-in MiniJinja templating

- Add MiniJinja dependency for Jinja2-compatible templating
- Create new project_template.rs module for template rendering
- Bundle snowflake template in templates/snowflake/ directory
- Remove dependency on external cookiecutter Python tool
- Handle Gitea publishing natively in Rust instead of Python hooks
- Update default template path to use bundled template with fallback
- Update README to reflect new built-in templating
- All tests pass

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

templates/snowflake/{{ cookiecutter.project_name }}/04-Outline/scene_breakdown/act_02.md

@@ -0,0 +1,11 @@
+## Act II – Confrontation (≈ 50 % of the story)
+
+<!-- First Plot Point: A decisive event propels the hero into a new world or situation (often a “point of no return”). Raises the stakes and moves the narrative firmly into the central conflict. -->
+
+<!-- Rising Action / Obstacles: Series of challenges, setbacks, and revelations that test the hero’s resolve. Builds tension, deepens character development, and expands the story’s scope. -->
+
+<!-- Midpoint: A major turning point—often a revelation, victory, or crisis—that changes the hero’s understanding or strategy. Re‑energizes the plot; the hero’s goal may shift or become clearer. -->
+
+<!-- Complications & Darkest Moment: Stakes intensify; the hero may suffer a major loss or face apparent defeat. Heightens emotional investment and sets up the need for a final push. -->
+
+<!-- Second Plot Point: The hero discovers a crucial piece of information or makes a decisive plan that leads to the climax. Provides the catalyst for the ultimate confrontation in Act III. -->