Configurable level and stat/experience gain charts

[Volte6]

Configurable Character Progression + Admin Visual Editor

Replaces all hardcoded character progression constants with a fully configurable system and adds a new /admin/progression page with live charts, interactive controls, and hover tooltips.

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Config (GamePlay.Progression.*)

• New ProgressionConfig struct under GamePlay exposes every previously hardcoded progression constant as a named config key
• Stat gains — BaseModFactor, BaseModExponent, NaturalGainsModFactor, NaturalGainsExponent control the racial and flat per-level stat growth curves; exponent fields allow linear, diminishing-returns, or accelerating shapes
• HP/Mana formulas — HPBase, HPPerLevel, HPPerVitality, ManaBase, ManaPerLevel, ManaPerMysticism
• Level-up rewards — TrainingPointsPerLevel, TrainingPointsEveryNLevels, StatPointsPerLevel, StatPointsEveryNLevels; the EveryNLevels fields allow burst-style rewards (e.g. 3 points every 2 levels)
• XP curve — XPBase, XPLevelFactor, XPLevelPower (capped at 5.0 to prevent integer overflow)
• Stat cap compression — StatCapThreshold, StatCapAnchor, StatCapExponent, StatCapScale, StatCapExemptBonus; when StatCapExemptBonus is enabled, only racial gains are compressed and training/equipment bonuses land on top at full value
• Display — MaxLevel for chart range
• All defaults reproduce the previous hardcoded behavior exactly; existing characters are unaffected by the migration

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Engine changes

• internal/stats/stats.go — GainsForLevel now uses math.Pow with the exponent knobs; Recalculate applies the configurable cap formula; new NoCap bool field on StatInfo lets HealthMax/ManaMax bypass the stat cap (previously they were incorrectly subject to it)
• internal/characters/character.go — XPTL, LevelUp, and RecalculateStats all read from GetProgressionConfig(); XPTL now uses float64 throughout (removing a float32 cast that caused negative XP display at high levels) and clamps the result to math.MaxInt64 before the int conversion
• internal/users/userrecord.go — level-up event accumulator now snapshots TrainingPoints/StatPoints before and after each LevelUp() call and diffs them, replacing hardcoded += 1 that ignored config
• internal/usercommands/experience.go — experience chart command now uses ValueAdj (compressed effective stat) instead of raw GainsForLevel, so the table matches what the game actually uses

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Admin page (/admin/progression)

• New page at /admin/progression with a sticky left control panel and a live chart column
• Controls — sliders and number inputs for every ProgressionConfig field, grouped into four sections (Stat Gains, HP & Mana, XP Curve, Level-Up Rewards); charts update 150ms after any change without saving
• Level-Up Rewards UX — each reward type is a self-contained card with an inline "Give N points every N levels" sentence and a live plain-English summary (e.g. "1 training point awarded every 3 levels (levels 3, 6, 9…)")
• ? tooltips — every control has a styled CSS tooltip explaining its intended effect and example use cases; tooltips are not clipped by the panel (overflow: hidden removed and replaced with targeted border-radius on first/last children)
• Four canvas charts — Stat Gains per Level (solid = raw Value, dashed = ValueAdj after cap), HP & Mana at Level, XP Required per Level, XP Cumulative; all redrawn on resize via ResizeObserver; data is computed server-side so charts are guaranteed to match the engine
• Chart interactivity — hovering any chart shows a vertical crosshair, dots on each series, and a floating tooltip with all series values at that level
• Save / Reset / Restore Defaults — Save patches the live config; Reset reverts unsaved slider changes; Restore Defaults opens a confirmation modal then saves all fields back to their hardcoded defaults
• Warning banner at the top of the page noting that changes are immediate, server-wide, and cannot be automatically reversed
• Preview API — GET /admin/api/v1/progression/preview accepts all config fields as query params, runs the actual Go formulas, and returns precomputed chart series (downsampled to ≤100 points regardless of MaxLevel)

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Bug fixes

• HealthMax and ManaMax were incorrectly subject to the stat cap compression formula; fixed via StatInfo.NoCap
• Level-up event TrainingPoints/StatPoints counts were hardcoded to 1 regardless of config
• experience chart command showed raw Value instead of compressed ValueAdj
• XPTL used a float32 cast that caused precision loss and negative XP display above ~level 150; now fully float64
• XPLevelPower validation cap lowered from 10.0 to 5.0 to prevent integer overflow at high levels with steep curves