Break v3 into 16 tickets

One file per feature, in the v2 shape that worked: goal, context, design,
implementation, acceptance criteria, tests, risks, out of scope -- written before
implementing so the risks are on paper rather than walked into.

Three carry more weight than their size suggests. V3-01 ships the port's first
real migration, and since the destructive fallback is gone, getting addColumn and
a v1-database test right matters more than the feature. V3-08 forces a
routing-engine decision with ongoing cost, so it sits behind a RoutingService
interface mirroring what LocationSource did for GPS. V3-13 is not code at all --
it answers the three questions open since v2, and V3-15 may close unbuilt as a
result, which is a legitimate outcome.

Several tickets record constraints that are easy to lose: no activity picker in
front of Start, because the founding premise is press-and-go with gloves; the
Route-to-Trip foreign key must not cascade, or deleting an old plan deletes the
ride; V3-14 will deliberately break the parity harness by adding GPX <type>, and
that expectation should be updated rather than the check dropped; and V3-16 must
not regress the explicit text colours that exist because of the black-on-black bug.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/v3/V3-13-real-ride-measurements.md

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+# V3-13 — Real-ride measurements: elevation, battery, map lifecycle
+
+**Phase** Quality · **Depends on** the real-ride checklist · **Size** M · **Status** Blocked on riding
+
+## Goal
+Answer three questions that no amount of code can answer, then act on the answers.
+
+## Context
+Three items have been carried since v2 because **nothing but a real ride settles them**.
+Grouped into one ticket because they share a prerequisite: riding, with instruments.
+
+## The three questions
+
+### 1. Is elevation gain actually wrong?
+~30 m of phantom gain per ten stationary minutes against **synthetic ±8 m uniform noise**.
+Real GPS altitude error is *correlated* — it wanders rather than jitters — so the true
+behaviour is unknown.
+
+**Do not tune this blind.** Record a flat ride and see what it reports. Only then consider
+a longer smoothing window, a larger threshold, or the barometer — which most phones have
+and which is far more accurate than GPS altitude.
+
+The port has an advantage the native app did not: `tool/parity/run.sh` proves the algorithm
+is bit-identical to the Kotlin original, so any change can be measured against a known
+baseline rather than guessed at.
+
+### 2. What does it actually cost in battery?
+Never measured, on either app. And V3-04/V3-05 make it worse: a lit screen and continuous
+map rendering are a different order of cost from a background service.
+
+Measure three configurations over a multi-hour ride: pocketed with no map, pocketed with
+the live map on, and mounted with the screen awake.
+
+### 3. Does the map leak?
+`flutter_map`'s lifecycle was wired carefully but never leak-tested across repeated
+navigation. The native repo flagged the osmdroid equivalent as a known hazard.
+
+## Implementation
+1. Run the checklist in [../port/REAL-RIDE-CHECKLIST.md](../port/REAL-RIDE-CHECKLIST.md)
+2. Record elevation on a known-flat route; compare against a barometric or surveyed source
+3. Battery: note the percentage at start and end for each configuration, with duration
+4. Memory: navigate rides → detail → back fifty times with DevTools attached, watching
+   for monotonic growth
+5. **Write the numbers into this file.** The point is a record, not a vibe.
+
+## Acceptance criteria
+- [ ] Flat-ride elevation gain recorded, with a verdict: acceptable or not
+- [ ] Battery cost per hour recorded for all three configurations
+- [ ] Memory across fifty navigations recorded, with a leak verdict
+- [ ] Any resulting code change is justified by a number written down here
+
+## Tests
+Measurement, not tests. Any fix that follows gets its own regression test, and elevation
+changes must be re-checked against the parity harness.
+
+## Risks
+The temptation to tune elevation on a hunch. The v2 backlog says do not, twice, and the
+existing bound was already shown to pass on seed luck.
+
+## Out of scope
+Fixes themselves. This ticket produces evidence; the fixes are separate work.